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Hospital costs of revascularization procedures for femoropopliteal arterial disease
Hospital costs of revascularization procedures for femoropopliteal arterial disease Maria G. M. HWlink, MD, PhD, Kimberly A. Cullen, BA, and Magruder C. Donaldson, MD, Boston) Mass. Purpose: On the basis of analyses performed 8 to 10 years ago, hospital costs for percutaneous transluminal angioplasty were believed to be no more than one third those of bypass. Given increasing awareness of cost as an important component in management decisions, updated information is needed. Methods: From 1985 to 1991, clinical and hospital cost data were collected prospectively for 255 admissions for femoropopliteal bypass and 82 for femoropopliteal angioplasty. Mean hospital costs and length of stay per admission were calculated for subgroups of patients defined by procedure and indication, and multiple regression analysis was performed. Results: For all admissions the mean hospital cost for angioplasty was $16,341 and for bypass it was $17,076 (nonsignificant difference). Excluding admissions associated with additional procedures, angioplasty cost on average $8019 and bypass $13,439, a significant difference (p = 0.0001). Stratification by indication demonstrated a significant difference for patients with disabling claudication (p = 0.0001), but the difference was of borderline significance for patients with critical ischemia (p = 0.08). An increasing trend in costs for angioplasty of $ 1270/yr was demonstrated during the study period, whereas the costs for bypass decreased by $370/yr. Conclusion: In contrast to what has been reported previously, the ratios of hospital costs of angioplasty to bypass were 53% for patients with disabling claudication and 75% for those with critical ischemia. (J VAse SURG 1994;19:632-41.)
Revascularization procedures (i.e., percutaneous transluminal angioplasty [PTA] and bypass) are generally considered effective treatments for peripheral arterial disease in patients with claudication or resting ischemic symptoms. 1-4 The decreasing risk of interventions, especially with the introduction of PTA, may broaden the indications for revascularization. However, there is controversy about the appropriate use of these technologies, particularly among patients with less severe disease. A decision and From the Deparnnent of Radiology (Dr. Hunink), CHASE Management Systems (Ms. Cullen), and the Deparnnent of Surgery (Dr. Donaldson), Brigham and Women's Hospital, Harvard Medical School; and the Deparnnent of Health Policy and Management (Dr. Hunink) , Harvard School of Public Health, Boston. Supported by an award from General Electric Radiology Research Academic Fellowships. Reprint requests: Maria G. M. Hunink, MD, PhD, Deparnnent of Health Sciences-PIONIER, Faculty of Medicine, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands. Copyright © 1994 by The Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter. 0741-5214/94/$3.00 + 0 24/1/49423
632
cost-effectiveness analysis of revascularization for peripheral arterial disease published in 1984 showed greater cost-effectiveness of PTA as the initial treatment whenever technically feasible, although less strikingly for femoropopliteal than for aortoiliac disease, reserving bypass for failure or recurrence after PTA.5 A more recent study of the impact of revascularization procedures has shown an increased use during the past 10 years in association with an enormous rise in the use of health-care resources. However, the data failed to demonstrate a significant decline of the amputation rate, thereby suggesting a limited benefit of revascularization_ 6,7 Although the methods used in the latter study were subject to a great deal of controversy,8-13 the conflicting results between the cost-effectiveness analysis published in 1984 and the recent studyS,6 suggest the need for a more extensive evaluation of risks, benefits, and costs that will assist in choosing the optimal treatment strategy for patients with peripheral arterial disease. 14 More data regarding the costs associated with peripheral revascularization procedures are required. The costs of PTA have generally been considered to be much lower than those of bypass on the basis
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Hunink, Cullen, and Donaldson 633
Table 1. Review of the costs/charges for PTA and bypass published in previous reports Reference, yr, cost/cha1lfe studied, procedure Doubilet and Abrams 5 ; 1982 hospital charges Angiogram plus PTA Angiogram plus bypass Wolf and McLean15 ; 1982 hospital charges Femoral PTA Femoral bypass Kinnison et al. 16 ; 1983 hospital charges Femoral PTA Femoral bypass Jeans et alY; 1984 hospital costs, from United Kingdomt Angiogram plus PTA Angiogram plus bypass
1990 U.S. dollars*
Ratio of costs PTA/bypass (%)
3,318 17,829
19
17,354 55,449
34
4,483 13,281
31
322 1,475
21
*Converted to 1990 U.S. dollars according to the medical component of the consumer price index (Bureau of Labor Statistics, U.S. Department of Labor). tl984 pounds were converted to 1984 dollars at an exchange rate of 1.336£/$ (International Monetary Fund).
of analyses performed 8 to 10 years ago (Table More recent cost analyses have focused on bypass and amputation but not on PTA 18 -21 Furthermore, current economic analyses of data on infrainguinal bypass usually use charges as an approximation of costs. 18 -21 As has been pointed out previously, costs and charges are not equivalent. 22,23 This article presents an analysis of hospital costs associated with PTA and bypass for the treatment of femoropopliteal disease, focusing on the differences between PTA and bypass and identifying the factors that influence costs.
1).5,15-17
METHODS Patient population All patients admitted to Brigham and Women's Hospital Vascular Surgery Service for femoropopliteal PTA or bypass between Oct. 1, 1985, and Oct. 31, 1991, were included in this study. The cohort described here overlaps with several previously described cohorts, of which efficacy results have been published. 2 ,24-27 Clinical data were collected prospectively and recorded in a computerized registry database. Prospective data on hospital costs and length of stay were recorded in the hospital inpatient database for the purpose of hospital accounting and management. Data on admissions for femoropopliteal revascularization from the two databases were matched by medical record number and procedure date. Both clinical and cost data were complete for 95% of all procedures performed. Information was available on 255 admissions of 228 patients for bypass and 82 admissions of7l patients for PTA. The study was approved by the institutional review board
and informed consent was obtained from every patient. All patients underwent diagnostic angiography. Choice of treatment was determined by clinical examination, noninvasive tests, and diagnostic angiography, after consultation between an interventional radiologist and vascular surgeon. Although no prospective selection criteria were used for either procedure, angioplasty was usually performed for focal disease of less than 5 cm when considered technically feasible, in patients with limb-threatening (critical) ischemia considered to be at high risk for systemic complications of surgery, and in those with disabling claudication.24 Bypass was performed in patients with diffuse disease, provided the risk of systemic complications was acceptable, and in those ineligible for PTA because of anatomic or technical considerations. 2,24-27 Management strategies included the preferential use of autologous vein for grafts and the optimal use of percutaneous techniques (PTA and thrombolysis) as adjuncts to operative techniques. A technically failed PTA or recurrent symptoms after PTA were generally treated with bypass, although in a few selected cases repeat PTA was performed. Covariates analyzed were age, sex, diabetes mellitus requiring treatment with insulin or oral hypoglycemic drugs, current smoking, treated or untreated hypertension, coronary artery disease (including coronary artery bypass grafting, history of myocardial infarction, or angiographically documented coronary artery disease), indication for the procedure, lesion type (occlusion vs stenosis), distal runoff (poor [zero or one vessel patent] versus good [two or three vessels patent]), number of lesions
634 Hunink, Cullen, and Donaldson
treated (multiple vs single lesion), repeat versus primary procedure, thrombolysis, second revascularization procedure during the same admission, and bypass graft material (autologous vein vs polytetrafluoroethylene). Thirty-day procedural complications recorded included death, nonfatal major systemic morbidity (nonfatal cardiac, pulmonary, cerebrovascular, septic, allergic, or renal complications), and nonfatal local morbidity (hematoma, wound infection, pseudoaneurysm, thrombosis, embolus, and early unplanned amputation). Hospital costs and length of stay Hospital costs included routine room and board, intermediate and intensive care room and board, operating room services (including nonprofessional anesthesia services), diagnostic angiography, interventional radiology, other diagnostic radiology services, clinical laboratory services (e.g., chemistry, hematology, and microbiology), patient laboratory services (e.g., noninvasive testing and electrocardiography), pharmacy and blood bank, and all other inpatient services immediately related to the admission (e.g., physical therapy, hemodialysis, and respiratory therapy). Physician fees were excluded from this analysis. Costs were calculated per patient and expressed in U.S. 1990 dollars with the use of the consumer price index. 28 Hospital administrative and accounting systems generally record charges to patients and payments received but seldom the actual cost per admission. Costs and charges are not equivalent: charges will exceed costs if a profit is desired and especially if reimbursements are a fraction of what is charged. For the purpose of economic evaluation of health-care practice, actual costs, not charges, are required. 22,23 Ideally, an extensive costing procedure identifying and quantifying each cost incurred is performed, but this is cumbersome, time-consuming, and costly. An alternative method, used in the current analysis, calculates costs per patient according to the ratio of costs to charges (RCC). This method entails the following steps: (1) Patient services are divided into centers that generate revenue, such as each specific ward, and various components of the operating room, anesthesia, radiology, and laboratory services. (2) The hospital calculates RCCs for each of these revenue centers retrospectively each year by dividing the center's total annual costs by its total annual charges, implying that an RCC is specific for a revenue center and year. (A center's total annual costs include direct costs associated with the specific revenue center and indirect costs associated with
JOURNAL OF VASCULAR SURGERY April 1994
general services that do not provide revenue such as transportation, heating, and housekeeping.) Indirect costs are distributed over all revenue centers according to criteria such as usage rate (e.g., for transportation) and square footage (e.g., for housekeeping). A center's total annual charges reflect all activities performed by that center and include both patientbased (e.g., a diagnostic test performed by radiology) and non-patient-based activities (e.g., help provided by the computing department, which is charged to the requesting department). The RCC therefore reflects the center's costs compared with activities performed and services provided. (3) A revenue center's RCC multiplied by the total charges billed to a patient by that specific service provides an estimate of the total cost for the patient to that service. (4) The cost of a specific patient hospitalization is calculated by distributing the patient's total charges into their revenue centers. Subsequently, the charges and RCC of each revenue center are multiplied. For example, if a patient is charged $1300 for a day of routine room and board and the specific RCC for the ward that year is 0.75, the actual cost for a day of room and board is estimated at $1300 X 0.75 = $975. Finally, the products for each revenue center are summed to find the total estimated cost of the hospitalization. Length of stay was determined as the number of days from date of admission to the date of discharge. Data analysis Patients undergoing PTA versus bypass were compared in univariate analysis for differences in covariates, with the t test and chi-squared test. Admissions were compared with the chi-squared test for differences in indication, additional unrelated procedures and additional related vascular procedures performed during the same admission, and 30-day morbidity and mortality rates. Vascular procedures not directly related to the femoropopliteal revascularization, such as carotid endarterectomy, coronary artery bypass, abdominal aortic aneurysm repair, bifurcation protheses, and aortorenal bypass, were considered unrelated procedures. Other unrelated major procedures performed during the same admission included percutaneous heart valvuloplasty, cholecystectomy, splenectomy, nephroureterectomy, gastrostomy, cystotomy, upper limb endarterectomy, and open reduction and internal fixation of the femur. Additional related vascular procedures performed were additional bypass, additional angioplasty, and thrombolysis. Hospital costs for PTA and bypass were first compared for all admissions. Costs were then calcu-
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lated for admissions with and without unrelated major procedures. Subsequently, excluding admissions with unrelated procedures, the costs for PTA and bypass were compared for subgroups defined by whether additional related vascular procedures were performed, indication, and whether debridement or amputation was performed, with the t test. Length of stay was analyzed in a similar fashion. To identify those covariates that affect costs and determine the magnitude of the effects, multiple linear regression analyses were performed. All admissions were included, and hospital costs and length of stay were modeled as dependent variables and the covariates as independent variables. The covariates in the model predicting costs were chosen by stepwise selection, evaluating all variables significant on univariate analysis and forcing the primary procedure performed into the model. The primary procedure was forced into the model to determine whether a difference exists between the procedures while adjusting for other significant variables. The model predicting length of stay included all covariates used in the final cost model. The significance of the parameters in the multiple regression analyses was determined with the Wald test. To determine the incremental cost and length of stay per admission associated with the outcome morbidity/mortality, a multiple regression analysis was performed including morbidity/mortality as an independent variable and adjusting for the significant covariates. Similarly, to determine the incremental cost for an additional day in the hospital, we included length of stay as an independent variable in the model. The components of the total costs were analyzed by indication and procedure, excluding admissions with additional related vascular procedures or unrelated procedures. The costs were analyzed by year, and multiple linear regression analysis was used to determine whether a trend over time was present. For all analyses a p value < 0.05 was considered significant and between 0.05 and 0.10 of borderline significance. A small proportion of patients was admitted more than once, which violates the assumption of independence of the observations in the statistical analyses. To examine whether this affected the results, a covariate was added indicating whether the admission was for a secondary procedure. This covariate was not significant in predicting mean cost or length of stay per admission. Second, the data were reanalyzed randomly selecting one admission per patient. Although the mean values and the parameters in the multiple regression analyses changed slightly, the
Hunink) Cullen) and Donaldson 635
Table II. Prevalence of cardiovascular risk factors in patients undergoing femoropopliteal PTA and bypass from 1985 to 1991 PTA
Bypass
Risk factor
(n = 71)
(n = 228)
Mean age (yr) Male (%) Coronary heart disease (%) History of smoking (%) Hypertension (%) Diabetes mellitus (%)
64.6 44 48 58 62 52*
66.4 55 44 64 56 33*
*x2 test (p
= 0.003).
same covariates demonstrated significance, the results were very similar, and the conclusions remained unchanged. Because the differences were inconsequential, the results reported are based on all admissions. RESULTS There was no significant difference in mean age, sex, presence of coronary artery disease, history of smoking, or hypertension among patients undergoing PTA compared with those undergoing bypass (Table II). Diabetes mellitus occurred significantly more often among those undergoing PTA. The indication for admission was significantly different (p = 0.01) between the two procedures, disabling claudication being the predominant indication (60% of admissions) for PTA and critical ischemia for bypass (57% of admissions). The mean ankle/brachial index before PTA was 0.58 (SD 0.14) among patients with disabling claudication and 0.41 (SD 0.21) among those with critical ischemia. Before bypass the index was 0.58 (SD 0.15) among patients with disabling claudication and 0.54 (SD 0.44) among those with critical ischemia. Multiple lesions were present in 39% of PTA cases, occlusions in 12%, poor runoff in 48%, and a distal lesion (popliteal artery) in 13%. Among surgical cases, multiple lesions were present in 84%, occlusions in 97%, and poor runoff in 30%, and in 57% a below-knee femoropopliteal bypass was performed. Seventeen percent of the bypasses were synthetic (polytetrafluoroethylene) as opposed to autologous vein. Eight and a half percent of admissions for PTA and 16% of those for bypass were for secondary procedures. Six (7%) of the 82 admissions for PTA and 18 (7%) of the 255 admissions for bypass were associated with additional major procedures not related directly to the femoropopliteal revasculariza-
JOURNAL OF VASCULAR SURGERY April 1994
636 Hunink, Cullen, and Donaldson
Table III. Mean hospital costs for femoropopliteal PTA and bypass depending on the type of admission Costs ± SD (U.s. 1990 dollars)
No. of admissions Type of admission/indication All admissions With unrelated major procedure(s)* Without unrelated major procedure(s) Without additional vascular procedures Claudication Critical Ischemia Without debridement/amputation With debridement/amputation With additional vascular proceduresll Claudication Critical Ischemia Without debridement/amputation With debridement/amputation
PTA
Bypass
PTA
82 6 76 39
255 18 237 206
16,341 35,198 14,852 8,019
25 14 10
96 110 90
6,152 ± 3,243t 11,353 ± 7,658:j: 8,543 ± 4,154§
11,582 ± 5,624t 15,059 ± 7,313:j: 13,858 ± 6,940§
4
20
18,380 ± 10,497
20,466 ± 6,602
37 22 15 8
31 11 20 18
22,054 14,680 32,869 17,062
19,934 17,288 21,389 20,820
7
2
± ± ± ±
± ± ± ±
16,729 29,963 14,550 5,753t
17,384 6,641 22,365 6,149
50,935 ± 20,226
Bypass 17,076 53,782 14,288 13,439
± ± ± ±
± ± ± ±
18,754 53,218 7,998 6,791 t
12,256 4,705 14,806 15,007
26,515 ± 16,679
*Coronary artery bypass grafting (n = 5), percutaneous heart valvuloplasty (n = 1), carotid endarterectomy (n = 2), abdominal aortic aneurysm repair or bifurcation protheses (n = 11), aortorenal bypass surgery (n = 1), cholecystectomy (n = 2), splenectomy (n = 1), nephroureterectomy (n = 1), gastrostomy (n = 1), cystotomy (n = 1), upper-limb endarterectomy (n = 1), and open reduction and internal fixation of the femur (n = 1). Note that some admissions were associated with more than one additional procedure. tp = 0.0001. :j:p = 0.08. §p = 0.02. IIAdditional bypass (n = 47), additional angioplasty (n = 21), and additional thrombolysis (n = 21). Note that some admissions were associated with two additional revascularization procedures.
tion (Table III). Additional PTA during the same admission took place in a minority of cases and no difference was noted between PTA (5%) and bypass surgery (7%). Additional bypass and thrombolysis were performed more commonly in association with PTA (34% and 16%) than with initial bypass (3% and 7%) (p s 0.0002). Six patients in the PTA group (7%) and 23 in the surgical group (9%) underwent an additional procedure because of complication or failure of the first (no significant difference). One patient died within 30 days in each group. Overall30-day major systemic or local morbidity and death occurred in 9% of admissions for PTA and 18% of admissions for bypass, a significant difference (p = 0.04). For all admissions the mean hospital costs for PTA and bypass were $16,341 and $17,076, respectively (Table III). The cost for admissions associated with unrelated procedures varied enormously because of the variability of the additional procedures performed. Excluding admissions with unrelated procedures, PTA cost $14,852 (SD $14,550) and bypass $14,288 (SD $7998) (no significant difference). Excluding additional unrelated procedures and related vascular procedures, PTA cost $8019 (SD
$5753) and bypass $13,439 (SD $6791) (p = 0.0001). With these exclusions and stratifying by indication, the mean hospital costs for PTA were significantly lower than those for bypass surgery for patients with claudication (p = 0.0001). The difference in costs between PTA and bypass surgery for patients treated for critical ischemia was of borderline significance (p = 0.08). No significant differences could be demonstrated for admissions for multiple revascularization procedures. Bypass surgery and PTA were performed in 42 cases; cost without thrombolysis was $21,244 (SD $15,529) and with thrombolysis $30,639 (SD $19,967). Admissions associated with an additional procedure for treatment of a complication or failure cost on average $46,245 (SD $23,340; n = 6) for PTA and $25,010 (SD $17,865; n = 23) for bypass (p = 0.02). Note that these results are subject to bias because the groups were determined retrospectively. Furthermore, the groups were too small to stratify meaningfully: five of the six PTA admissions and 19 of the 23 surgical admissions were for critical ischemia. Mean hospital costs and length of stay were highly correlated (R2 = 0.89; P = 0.0001). Excluding additional unrelated and related vascular procedures, the mean length of
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Hunink, Cullen, and Donaldson 637
Table IV. Incremental mean hospital costs and length of stay per admission determined with multiple regression for various factors for femoropopliteal revascularization including all admissions (n = 337) Factor* Bypass vs PTA Additional unrelated procedures:j: Additional related vascular procedures§ Debridement or amputation
Incremental mean cost and SE (US. 1990 dollars) (p valuet) 5,038 28,137 9,003 24,766
± 1,817 2,881 ± 1,868 ± 2,241
±
Incremental length of stay and SE (days) (p valuet) 6.3 20.6 6.0 24.0
(0.006) (0.0001) (0.0001) (0.0001)
± 1.8 (0.0004) ± 2.8 (0.0001) ± 1.8 (0.001) ± 2.2 (0.0001)
*Adjusted for the primary procedure performed, additional unrelated procedures, additional related vascular procedures, and debridement or amputation. The intercepts for the models were $5964 (SE $1767) for costs and 2.6 (SE 1.7) days for length of stay. The R2 was 0.47 for the cost model and 0.41 for the length of stay. tWald test for significance in multiple regression model. §Additional bypass, additional angioplasry, and thrombolysis. :j:Coronary artery bypass grafting, percutaneous heart valvuloplasty, carotid endarterectomy, abdominal aortic aneurysm repair, and other major surgery (see footnote Table III).
Table V. Components of the mean hospital costs per admission for femoropopliteal PTA and bypass* Mean cost in 1990 US. dollars (% of total cost) Critical ischemia
Claudication Component Procedural costs Diagnostic angiography/interventional radiology Operating room and anesthesia Hotel costs Routine room and board Intermediate/intensive care Supportive Diagnostic radiology (other than angiography) Clinical laboratory servicest Patient laboratory services:j: Pharmacy and blood bank§ Miscellaneous otherll Total
Bypass (n = 96)
PTA (n = 14)
(n
5,008 (81) o (0)
2,340 (20) 3,800 (33)
4,358 (38) 283 (3)
2,120 (14) 4,325 (29)
814 (13) o (0)
4,077 (35) 144 (1)
3,694 (33) 428 (4)
5,575 (37) 890 (6)
PTA (n = 25)
32 87 97 101 13 6,152
«1) (1) (2) (2) «1)
144 262 194 482 136 11,582
(1) (2) (2) (4) (1)
93 434 216 1,497 351 11,353
(1) (4) (2) (13) (3)
Bypass = 110)
243 485 293 799 328 15,059
(2) (3) (2) (5) (2)
*Excluding admissions associated with additional major procedures (additional bypass, additional angioplasty, thrombolysis, coronary artery bypass grafting, percutaneous heart valvuloplasty, carotid endarterectomy, abdominal aortic aneurysm repair, and other major surgery [see footnote Table III». Physicians' professional fees are excluded from the analysis. tlncludes chemistry, hematology, and microbiology. :j:lncludes noninvasive testing and electrocardiography. §Includes medications, intravenous solutions, and transfusions. IIlncludes inpatient rehabilitation, hemodialysis, and respiratory therapy.
stay was significandy different for PTA compared with bypass (4.2 vs 11.3 days; p = 0.0001). For patients with claudication the mean length of stay was significandy lower for PTA than for bypass (1.8 vs 9.3 days; p = 0.0001). For admissions for critical ischemia the difference in length of stay was of borderline significance (8.6 vs 13.0 days;p = 0.05). With multiple linear regression the incremental mean hospital costs and length of stay depending on the presence of various factors were determined for all admissions (Table IV). The significant covariates in
predicting mean hospital cost were the primary procedure, additional unrelated procedures, additional related vascular procedures, and whether debridement or amputation was performed during the same admission. Although a significant difference in indication and the prevalence of diabetes existed between patients treated with bypass versus PTA, neither was significant in predicting costs in the multiple regression analysis adjusting for the significant factors. This is probably because the effects of both indication and diabetes mellitus are reflected by
638 Hunink, Cullen, and Donaldson
whether debridement or amputation is performed. Mean costs and length of stay were influenced significantly by the outcome of morbidity or death, which increased hospital costs per admission by $13,065 (SE $1918;p = 0.0001) and length of stay by 11.1 days (SE 1.9;p = 0.0001). With adjustment for the primary procedure, additional related vascular procedures, additional unrelated procedures, debridement or amputation, and morbidity/mortality, the incremental cost of 1 day in the hospital was $939 (SE $24;p = 0.0001). Excluding admissions with additional related vascular or unrelated procedures, analysis of the cost components (Table V) demonstrated that for patients treated for claudication the procedural costs (i.e., diagnostic angiography, interventional radiology, operating room, and anesthesia) constituted the major proportion of the total costs (81 % for PTA and 53% for bypass). On the other hand, for patients treated for critical ischemia, the procedural costs were the same proportion as hotel costs (i.e., routine room and board and intensive/intermediate care), each constituting approximately 40% of the total cost irrespective of the procedure. Supportive costs were less than 25% of the total costs irrespective of procedure and indication. The procedural costs were similar for PTA and bypass; however, hotel costs were lower for PTA. Multiple regression analysis of the hospital costs for PTA over time, with adjustment for the significant covariates, demonstrated an increase of $1269 (SE $731) per year (p = 0.08) because of an increase in the costs for angiography and interventional radiology (Fig. 1). In contrast, analysis of the hospital costs for bypass over time demonstrated a nonsignificant decrease of $369 (SE $313) per year (p = 0.24) (Fig. 2). Multiple regression analysis of the mean length of stay over time, with adjustment for the significant covariates, demonstrated no change for PTA and a decrease of 1.1 day per year (p = 0.0001) for bypass.
DISCUSSION Table I reviews previously reported cost and charge data for PTA and bypass performed for peripheral arterial disease. The highest figures are charges reported by Wolf and McLean. ls However, their data are biased because of a long average hospital stay of 8.5 days for PTA and 26.8 days for bypass and, as they state, "skewed by a few patients with very long hospital stays and hence large bills." The reported costs of bypass and PTA in the United Kingdom are substantially lower than those in the United States. S,IS.2I Caution must be exercised in
JOURNAL OF VASCULAR SURGERY April 1994
interpreting these figures because the studies from the United Kingdom l7,21 enumerate actual costs, whereas those from the United States S,IS,16,18-20 present charges. Comparison of our cost estimates with previously published figures from the United States is hampered by the same problem. In general, charges are not a good approximation of costs. 22 For example, at the Brigham and Women's Hospital the ratio of costs to charges ranges from 0.75 to 1.0 for routine room and board, is generally larger than 1.0 for intermediate and intensive care, is approximately 0.40 for operating room services, and is close to 1.0 for angiography. Rather than evaluate charges, we evaluated costs by a method that estimates costs relative to charges per service rendered. Overall, charges exceeded costs by 20% to 30% for admissions for PTA and 50% for bypass. A comparison of nonrandomized patients who have undergone PTA versus bypass inherently brings with it the question whether the groups are comparable. In this study PTA was performed for less severe disease, which in the nonstratified, nonadjusted analysis may bias the costs for PTA toward lower values. On the other hand, admissions for PTA were more commonly associated with additional bypass and thrombolysis, biasing the costs upward. To identify whether differences in the PTA and surgical groups translated into predictable cost differences, the analysis was performed stratified by indication and additional procedures, and a multiple regression analysis was performed. In this analysis lesion severity was not significant in predicting costs, probably because the effect of lesion severity was reflected in other variables. Long lesions (> 5 cm), multiple lesions, and nonfocal occlusions may increase the costs of PTA, but these types of lesions in the femoropopliteallocation are currently not generally considered amenable to PTA. Although lesion severity may influence the costs of PTA, it is difficult to conceive how lesion severity (independently) will impact on the costs of bypass other than through variables such as indication, additional procedures, debridement, and amputation. Eight to 10 years ago, the costs of PTA were 19% to 34% of the costs of bypass (Table I), suggesting that cost savings might be possible if PTA was deemed effective. S,15-I7 In contrast, this study found that PTA currently costs on average 60% of the cost of surgery, a far less favorable ratio. The average ratio of 60% is partly a reflection of the significant difference in indication between the PTA and surgical groups. For patients treated for disabling claudication, the cost advantage of PTA over bypass was
JOURNAL OF VASCULAR SURGERY Volume 19, Number 4
Hunink, Cullen, and Donaldson 639
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~ Intensive care
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significant: the cost of PTA is 53% that of a graft. For patients with critical ischemia, the difference in costs was of borderline significance, PTA costing 75% that of surgery. We attempted to explain why the ratio of PTA to that of bypass increased during the past 10 years. Analysis of the costs of PTA versus bypass suggested that the costs of PTA increased $1270 per year, whereas the costs of bypass decreased approximately $370 per year. Analysis of the cost compo-
nents suggested that for PTA the increase in cost was the result of an increase in cost of the actual procedure. A possible reason for the increasing costs of PTA could be the refinement of catheters and guide wires used during PTA or the use of more expensive (low-osmolar) contrast agents. For bypass, operating room expenses seemed to be more or less constant during the study period, the cost for diagnostic angiography increased, and hotel costs
640 Hunink, Cullen, and Donaldson
decreased. The latter observation agrees with the significantly decreased length of stay for bypass. This suggests that any increase in procedural or supportive costs for bypass was compensated by the decrease in hotel costs. For both bypass and PTA, hospital costs were dependent on the indication for the procedure. This finding is supported by Gupta and Veith, 20 who observed the same indication-dependent discrepancy in hospital charges for vascular surgery. In patients treated for critical ischemia, the difference in mean hospital costs of PTA and bypass was of borderline significance, suggesting that the costs of a hospital admission for revascularization for critical ischemia are determined mainly by adjuvant treatment and the cost of the actual procedure performed is a small proportion of the total costs. This hypothesis is supported by this study through (1) the stratified analysis, which demonstrated a significant difference for patients with ischemia if neither debridement nor amputation was performed; (2) the multiple regression analysis, which demonstrated that performing ulcer debridement or amputation was significant in predicting costs; and (3) the analysis of cost components, which demonstrated that the costs for the actual procedure were a smaller fraction of the total cost for patients with critical ischemia than for patients with claudication. In addition to indication, mean hospital costs for revascularization also correlated with complications and length of stay. Because the latter are outcomes and not independent variables, they were not included in the baseline regression analysis, because for meaningful decision making predictions of cost should be based on information available before the choice of procedure. However, including these as independent variables and with adjustment for the significant covariates, the incremental cost associated with complications and an extra day in the hospital were approximately $13,000 and $1000jday, respectively. In conclusion, the observation that PTA is not as inexpensive relative to bypass as it previously seemed to be, together with current reports of the efficacy of PTA based on strict outcome criteria and reporting standards,29 may necessitate a reassessment of the indications for PTA. A cost-effectiveness analysis comparing PTA with medical treatment and bypass may help resolve this issue. 5,7,11,22 Such an analysis needs to be stratified for varying severity of disease, at the least distinguishing patients by indication, because revascularization performed for critical ischemia has a higher risk, yields lower long-term
JOURNAL OF VASCULAR SURGERY April 1994
patency, and costs more than revascularization performed for claudication. Furthermore, whether the optimal treatment for claudication is intervention or conservative treatment requires clarification. However, some variables remain to be elucidated before a comprehensive reassessment and cost-effectiveness analysis of the treatment of peripheral arterial disease are feasible, including the long-term results of medical or conservative treatment and the improvement in quality of life after various forms of treatment. We acknowledge the assistance of Julie Lombara in retrieving clinical information on study patients. REFERENCES 1. Becker GJ, Katzen BT, DaKe MD. Noncoronary angioplasty. Radiology 1989;170:921-40. 2. Donaldson MC, Mannick JA, Whittemore AD. Femoraldistal bypass with in situ greater saphenous vein. Ann Surg 1991;213:457-65. 3. Johnston KW, Rae M, Hogg-Johnston SA, et al. Five-year results of a prospective study of percutaneous transluminal angioplasty. Ann Surg 1987;206:403-13. 4. Veith FJ, Gupta SK, W~ngerter KR, et al. Changing arteriosclerotic disease patterns and management strategies in lower-limb-threatening ischemia. Ann Surg 1990;212:40214. 5. Doubilet P, Abrams HL. The cost of underutilization: percutaneous transluminal angioplasty for peripheral vascular disease. N Engl J Med 1984;310:95-102. 6. Tunis SR, Bass EB, Steinberg EP. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease. N Engl J Med 1991;325:556-62. 7. Coffman JD. Intermittent claudication: be conservative. N Engl J Med 1991;325:577-8. 8. Pentecost MJ. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease [letter;comment]. N Engl J Med 1992;326:413. 9. Veith FJ, Peder BA, Bakal CWo Letter to the editor in response to Tunis SR, Bass EB, Steinberg EP. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease [letter]. N Engl J Med 1992;326:413-4. 10. Osterman FA Jr. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease [letter; comment]. N Engl J Med 1992;326:414. 11. Hunink MGM, Meyerovitz MF. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease [letter]. N Engl J Med 1992;326: 414. 12. Clugston RA, Eisenhauer AC, Matthews R V. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease [letter]. N Engl J Med 1992;326:415. 13. Becker GJ, Ferguson JG, Bakal CW, et al. Angioplasty, bypass surgery, and amputation for lower extremity peripheral arterial disease in Maryland: a closer look. Radiology 1993; 186:635-8. 14. McNeil B. The changing financial picture in health: impact on radiology and the use of new technologies. Eugene P.
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15.
16.
17.
18.
19.
20.
21.
22.
Pendergrass New Horiwns Lecture. Seventy-seventh Scientific Assembly and Annual Meeting of the Radiological Society of North America, December 1991. Wolf GL, McLean G. Comparison of the costs of bypass surgery and transluminal 'angioplasty for peripheral vascular disease. Semin Intervent Radiol 1984;1:237-9. Kinnison ML, White RI, Bowers WP, Dunlap ED. Cost incentives for peripheral angioplasty. AJR Am J Roentgenol 1985;145:1241-4. Jeans WD, Danton RM, Baird RN, Horrocks M. A comparison of the costs of vascular surgery and balloon dilatation in lower limb ischaemic disease. Br J Radiol 1986;59:453-6. Gupta SK, Veith FJ, Ascer E, White Flores SA, Gliedman ML. Cost factors in limb-threatening ischemia due to infrainguinal arteriosclerosis. Eur J Vase Surg 1988;2:151-4. Mackey WC, McCullough JL, Conlon TP, et aL The costs of surgery for limb-threatening ischemia. Surgery 1986;99:2635. Gupta SK, Veith FJ. Inadequacy of the diagnosis related group (DRG) reimbursements for limb salvage lower extremity arterial reconstructions. J VASC SURG 1990;11:348-57. Cheshire NJW, Wolfe JHN, Noone MA, Davies L, Drummond M. The economics of femorocrural reconstruction for critical leg ischemia with and without autologous vein. J VASC SURG 1992;15:167-75. Drummond MF, Stoddart GL, Torrance GW. Methods for the economic evaluation of health care programmes. Oxford: Oxford Medical Publications, 1987.
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23. Weinstein MC, Stason WB. Foundations of cost-effectiveness analysis for health and medical practices. N Engl J Med 1977;296:716-21. 24. Hunink MGM, Donaldson MC, Meyerovitz MF, et aL Risks and benefits of femoropopliteal percutaneous balloon angioplasty. J VASC SURG 1993;17:183-92. 25. Kent KC, Donaldson MC, Attinger CE, Couch NP, Mannick JA, Whitremore AD. Femoropopliteal reconstruction for claudication: the risk to life and limb. Arch Surg 1988;123: 1196-8. 26. Kent KC, Whitremore AD, Mannick JA. Short-term and midterm results of an all-autogenous tissue policy for infrainguinal reconstruction. J VASC SURG 1989;9:107-14. 27. Whitremore AD, Kent C, Donaldson MC, Couch NP, Mannick JA. What is the proper role of polytetrafiuoroethylene grafts in infraguinal reconstruction? J VASC SURG 1989;10:299-305. 28. Consumer price indexes, Bureau of Labor Statistics, U.S. Department of Labor. In: Hoffman MS, ed. The world almanac and book of facts 1992. New York: Pharos Books, 1991. 29. Rutherford RB, Becker GJ. Standards for evaluating and reporting the results of surgical and percutaneous therapy for peripheral arterial disease. Radiology 1991;181:277-81.
Submitred April 1, 1993; accepted June 12, 1993.
Revascularization procedures (i.e., percutaneous transluminal angioplasty [PTA] and bypass) are generally considered effective treatments for peripheral arterial disease in patients with claudication or resting ischemic symptoms. 1-4 The decreasing risk of interventions, especially with the introduction of PTA, may broaden the indications for revascularization. However, there is controversy about the appropriate use of these technologies, particularly among patients with less severe disease. A decision and From the Deparnnent of Radiology (Dr. Hunink), CHASE Management Systems (Ms. Cullen), and the Deparnnent of Surgery (Dr. Donaldson), Brigham and Women's Hospital, Harvard Medical School; and the Deparnnent of Health Policy and Management (Dr. Hunink) , Harvard School of Public Health, Boston. Supported by an award from General Electric Radiology Research Academic Fellowships. Reprint requests: Maria G. M. Hunink, MD, PhD, Deparnnent of Health Sciences-PIONIER, Faculty of Medicine, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands. Copyright © 1994 by The Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter. 0741-5214/94/$3.00 + 0 24/1/49423
632
cost-effectiveness analysis of revascularization for peripheral arterial disease published in 1984 showed greater cost-effectiveness of PTA as the initial treatment whenever technically feasible, although less strikingly for femoropopliteal than for aortoiliac disease, reserving bypass for failure or recurrence after PTA.5 A more recent study of the impact of revascularization procedures has shown an increased use during the past 10 years in association with an enormous rise in the use of health-care resources. However, the data failed to demonstrate a significant decline of the amputation rate, thereby suggesting a limited benefit of revascularization_ 6,7 Although the methods used in the latter study were subject to a great deal of controversy,8-13 the conflicting results between the cost-effectiveness analysis published in 1984 and the recent studyS,6 suggest the need for a more extensive evaluation of risks, benefits, and costs that will assist in choosing the optimal treatment strategy for patients with peripheral arterial disease. 14 More data regarding the costs associated with peripheral revascularization procedures are required. The costs of PTA have generally been considered to be much lower than those of bypass on the basis
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Hunink, Cullen, and Donaldson 633
Table 1. Review of the costs/charges for PTA and bypass published in previous reports Reference, yr, cost/cha1lfe studied, procedure Doubilet and Abrams 5 ; 1982 hospital charges Angiogram plus PTA Angiogram plus bypass Wolf and McLean15 ; 1982 hospital charges Femoral PTA Femoral bypass Kinnison et al. 16 ; 1983 hospital charges Femoral PTA Femoral bypass Jeans et alY; 1984 hospital costs, from United Kingdomt Angiogram plus PTA Angiogram plus bypass
1990 U.S. dollars*
Ratio of costs PTA/bypass (%)
3,318 17,829
19
17,354 55,449
34
4,483 13,281
31
322 1,475
21
*Converted to 1990 U.S. dollars according to the medical component of the consumer price index (Bureau of Labor Statistics, U.S. Department of Labor). tl984 pounds were converted to 1984 dollars at an exchange rate of 1.336£/$ (International Monetary Fund).
of analyses performed 8 to 10 years ago (Table More recent cost analyses have focused on bypass and amputation but not on PTA 18 -21 Furthermore, current economic analyses of data on infrainguinal bypass usually use charges as an approximation of costs. 18 -21 As has been pointed out previously, costs and charges are not equivalent. 22,23 This article presents an analysis of hospital costs associated with PTA and bypass for the treatment of femoropopliteal disease, focusing on the differences between PTA and bypass and identifying the factors that influence costs.
1).5,15-17
METHODS Patient population All patients admitted to Brigham and Women's Hospital Vascular Surgery Service for femoropopliteal PTA or bypass between Oct. 1, 1985, and Oct. 31, 1991, were included in this study. The cohort described here overlaps with several previously described cohorts, of which efficacy results have been published. 2 ,24-27 Clinical data were collected prospectively and recorded in a computerized registry database. Prospective data on hospital costs and length of stay were recorded in the hospital inpatient database for the purpose of hospital accounting and management. Data on admissions for femoropopliteal revascularization from the two databases were matched by medical record number and procedure date. Both clinical and cost data were complete for 95% of all procedures performed. Information was available on 255 admissions of 228 patients for bypass and 82 admissions of7l patients for PTA. The study was approved by the institutional review board
and informed consent was obtained from every patient. All patients underwent diagnostic angiography. Choice of treatment was determined by clinical examination, noninvasive tests, and diagnostic angiography, after consultation between an interventional radiologist and vascular surgeon. Although no prospective selection criteria were used for either procedure, angioplasty was usually performed for focal disease of less than 5 cm when considered technically feasible, in patients with limb-threatening (critical) ischemia considered to be at high risk for systemic complications of surgery, and in those with disabling claudication.24 Bypass was performed in patients with diffuse disease, provided the risk of systemic complications was acceptable, and in those ineligible for PTA because of anatomic or technical considerations. 2,24-27 Management strategies included the preferential use of autologous vein for grafts and the optimal use of percutaneous techniques (PTA and thrombolysis) as adjuncts to operative techniques. A technically failed PTA or recurrent symptoms after PTA were generally treated with bypass, although in a few selected cases repeat PTA was performed. Covariates analyzed were age, sex, diabetes mellitus requiring treatment with insulin or oral hypoglycemic drugs, current smoking, treated or untreated hypertension, coronary artery disease (including coronary artery bypass grafting, history of myocardial infarction, or angiographically documented coronary artery disease), indication for the procedure, lesion type (occlusion vs stenosis), distal runoff (poor [zero or one vessel patent] versus good [two or three vessels patent]), number of lesions
634 Hunink, Cullen, and Donaldson
treated (multiple vs single lesion), repeat versus primary procedure, thrombolysis, second revascularization procedure during the same admission, and bypass graft material (autologous vein vs polytetrafluoroethylene). Thirty-day procedural complications recorded included death, nonfatal major systemic morbidity (nonfatal cardiac, pulmonary, cerebrovascular, septic, allergic, or renal complications), and nonfatal local morbidity (hematoma, wound infection, pseudoaneurysm, thrombosis, embolus, and early unplanned amputation). Hospital costs and length of stay Hospital costs included routine room and board, intermediate and intensive care room and board, operating room services (including nonprofessional anesthesia services), diagnostic angiography, interventional radiology, other diagnostic radiology services, clinical laboratory services (e.g., chemistry, hematology, and microbiology), patient laboratory services (e.g., noninvasive testing and electrocardiography), pharmacy and blood bank, and all other inpatient services immediately related to the admission (e.g., physical therapy, hemodialysis, and respiratory therapy). Physician fees were excluded from this analysis. Costs were calculated per patient and expressed in U.S. 1990 dollars with the use of the consumer price index. 28 Hospital administrative and accounting systems generally record charges to patients and payments received but seldom the actual cost per admission. Costs and charges are not equivalent: charges will exceed costs if a profit is desired and especially if reimbursements are a fraction of what is charged. For the purpose of economic evaluation of health-care practice, actual costs, not charges, are required. 22,23 Ideally, an extensive costing procedure identifying and quantifying each cost incurred is performed, but this is cumbersome, time-consuming, and costly. An alternative method, used in the current analysis, calculates costs per patient according to the ratio of costs to charges (RCC). This method entails the following steps: (1) Patient services are divided into centers that generate revenue, such as each specific ward, and various components of the operating room, anesthesia, radiology, and laboratory services. (2) The hospital calculates RCCs for each of these revenue centers retrospectively each year by dividing the center's total annual costs by its total annual charges, implying that an RCC is specific for a revenue center and year. (A center's total annual costs include direct costs associated with the specific revenue center and indirect costs associated with
JOURNAL OF VASCULAR SURGERY April 1994
general services that do not provide revenue such as transportation, heating, and housekeeping.) Indirect costs are distributed over all revenue centers according to criteria such as usage rate (e.g., for transportation) and square footage (e.g., for housekeeping). A center's total annual charges reflect all activities performed by that center and include both patientbased (e.g., a diagnostic test performed by radiology) and non-patient-based activities (e.g., help provided by the computing department, which is charged to the requesting department). The RCC therefore reflects the center's costs compared with activities performed and services provided. (3) A revenue center's RCC multiplied by the total charges billed to a patient by that specific service provides an estimate of the total cost for the patient to that service. (4) The cost of a specific patient hospitalization is calculated by distributing the patient's total charges into their revenue centers. Subsequently, the charges and RCC of each revenue center are multiplied. For example, if a patient is charged $1300 for a day of routine room and board and the specific RCC for the ward that year is 0.75, the actual cost for a day of room and board is estimated at $1300 X 0.75 = $975. Finally, the products for each revenue center are summed to find the total estimated cost of the hospitalization. Length of stay was determined as the number of days from date of admission to the date of discharge. Data analysis Patients undergoing PTA versus bypass were compared in univariate analysis for differences in covariates, with the t test and chi-squared test. Admissions were compared with the chi-squared test for differences in indication, additional unrelated procedures and additional related vascular procedures performed during the same admission, and 30-day morbidity and mortality rates. Vascular procedures not directly related to the femoropopliteal revascularization, such as carotid endarterectomy, coronary artery bypass, abdominal aortic aneurysm repair, bifurcation protheses, and aortorenal bypass, were considered unrelated procedures. Other unrelated major procedures performed during the same admission included percutaneous heart valvuloplasty, cholecystectomy, splenectomy, nephroureterectomy, gastrostomy, cystotomy, upper limb endarterectomy, and open reduction and internal fixation of the femur. Additional related vascular procedures performed were additional bypass, additional angioplasty, and thrombolysis. Hospital costs for PTA and bypass were first compared for all admissions. Costs were then calcu-
JOURNAL OF VASCULAR SURGERY Volume 19, Number 4
lated for admissions with and without unrelated major procedures. Subsequently, excluding admissions with unrelated procedures, the costs for PTA and bypass were compared for subgroups defined by whether additional related vascular procedures were performed, indication, and whether debridement or amputation was performed, with the t test. Length of stay was analyzed in a similar fashion. To identify those covariates that affect costs and determine the magnitude of the effects, multiple linear regression analyses were performed. All admissions were included, and hospital costs and length of stay were modeled as dependent variables and the covariates as independent variables. The covariates in the model predicting costs were chosen by stepwise selection, evaluating all variables significant on univariate analysis and forcing the primary procedure performed into the model. The primary procedure was forced into the model to determine whether a difference exists between the procedures while adjusting for other significant variables. The model predicting length of stay included all covariates used in the final cost model. The significance of the parameters in the multiple regression analyses was determined with the Wald test. To determine the incremental cost and length of stay per admission associated with the outcome morbidity/mortality, a multiple regression analysis was performed including morbidity/mortality as an independent variable and adjusting for the significant covariates. Similarly, to determine the incremental cost for an additional day in the hospital, we included length of stay as an independent variable in the model. The components of the total costs were analyzed by indication and procedure, excluding admissions with additional related vascular procedures or unrelated procedures. The costs were analyzed by year, and multiple linear regression analysis was used to determine whether a trend over time was present. For all analyses a p value < 0.05 was considered significant and between 0.05 and 0.10 of borderline significance. A small proportion of patients was admitted more than once, which violates the assumption of independence of the observations in the statistical analyses. To examine whether this affected the results, a covariate was added indicating whether the admission was for a secondary procedure. This covariate was not significant in predicting mean cost or length of stay per admission. Second, the data were reanalyzed randomly selecting one admission per patient. Although the mean values and the parameters in the multiple regression analyses changed slightly, the
Hunink) Cullen) and Donaldson 635
Table II. Prevalence of cardiovascular risk factors in patients undergoing femoropopliteal PTA and bypass from 1985 to 1991 PTA
Bypass
Risk factor
(n = 71)
(n = 228)
Mean age (yr) Male (%) Coronary heart disease (%) History of smoking (%) Hypertension (%) Diabetes mellitus (%)
64.6 44 48 58 62 52*
66.4 55 44 64 56 33*
*x2 test (p
= 0.003).
same covariates demonstrated significance, the results were very similar, and the conclusions remained unchanged. Because the differences were inconsequential, the results reported are based on all admissions. RESULTS There was no significant difference in mean age, sex, presence of coronary artery disease, history of smoking, or hypertension among patients undergoing PTA compared with those undergoing bypass (Table II). Diabetes mellitus occurred significantly more often among those undergoing PTA. The indication for admission was significantly different (p = 0.01) between the two procedures, disabling claudication being the predominant indication (60% of admissions) for PTA and critical ischemia for bypass (57% of admissions). The mean ankle/brachial index before PTA was 0.58 (SD 0.14) among patients with disabling claudication and 0.41 (SD 0.21) among those with critical ischemia. Before bypass the index was 0.58 (SD 0.15) among patients with disabling claudication and 0.54 (SD 0.44) among those with critical ischemia. Multiple lesions were present in 39% of PTA cases, occlusions in 12%, poor runoff in 48%, and a distal lesion (popliteal artery) in 13%. Among surgical cases, multiple lesions were present in 84%, occlusions in 97%, and poor runoff in 30%, and in 57% a below-knee femoropopliteal bypass was performed. Seventeen percent of the bypasses were synthetic (polytetrafluoroethylene) as opposed to autologous vein. Eight and a half percent of admissions for PTA and 16% of those for bypass were for secondary procedures. Six (7%) of the 82 admissions for PTA and 18 (7%) of the 255 admissions for bypass were associated with additional major procedures not related directly to the femoropopliteal revasculariza-
JOURNAL OF VASCULAR SURGERY April 1994
636 Hunink, Cullen, and Donaldson
Table III. Mean hospital costs for femoropopliteal PTA and bypass depending on the type of admission Costs ± SD (U.s. 1990 dollars)
No. of admissions Type of admission/indication All admissions With unrelated major procedure(s)* Without unrelated major procedure(s) Without additional vascular procedures Claudication Critical Ischemia Without debridement/amputation With debridement/amputation With additional vascular proceduresll Claudication Critical Ischemia Without debridement/amputation With debridement/amputation
PTA
Bypass
PTA
82 6 76 39
255 18 237 206
16,341 35,198 14,852 8,019
25 14 10
96 110 90
6,152 ± 3,243t 11,353 ± 7,658:j: 8,543 ± 4,154§
11,582 ± 5,624t 15,059 ± 7,313:j: 13,858 ± 6,940§
4
20
18,380 ± 10,497
20,466 ± 6,602
37 22 15 8
31 11 20 18
22,054 14,680 32,869 17,062
19,934 17,288 21,389 20,820
7
2
± ± ± ±
± ± ± ±
16,729 29,963 14,550 5,753t
17,384 6,641 22,365 6,149
50,935 ± 20,226
Bypass 17,076 53,782 14,288 13,439
± ± ± ±
± ± ± ±
18,754 53,218 7,998 6,791 t
12,256 4,705 14,806 15,007
26,515 ± 16,679
*Coronary artery bypass grafting (n = 5), percutaneous heart valvuloplasty (n = 1), carotid endarterectomy (n = 2), abdominal aortic aneurysm repair or bifurcation protheses (n = 11), aortorenal bypass surgery (n = 1), cholecystectomy (n = 2), splenectomy (n = 1), nephroureterectomy (n = 1), gastrostomy (n = 1), cystotomy (n = 1), upper-limb endarterectomy (n = 1), and open reduction and internal fixation of the femur (n = 1). Note that some admissions were associated with more than one additional procedure. tp = 0.0001. :j:p = 0.08. §p = 0.02. IIAdditional bypass (n = 47), additional angioplasty (n = 21), and additional thrombolysis (n = 21). Note that some admissions were associated with two additional revascularization procedures.
tion (Table III). Additional PTA during the same admission took place in a minority of cases and no difference was noted between PTA (5%) and bypass surgery (7%). Additional bypass and thrombolysis were performed more commonly in association with PTA (34% and 16%) than with initial bypass (3% and 7%) (p s 0.0002). Six patients in the PTA group (7%) and 23 in the surgical group (9%) underwent an additional procedure because of complication or failure of the first (no significant difference). One patient died within 30 days in each group. Overall30-day major systemic or local morbidity and death occurred in 9% of admissions for PTA and 18% of admissions for bypass, a significant difference (p = 0.04). For all admissions the mean hospital costs for PTA and bypass were $16,341 and $17,076, respectively (Table III). The cost for admissions associated with unrelated procedures varied enormously because of the variability of the additional procedures performed. Excluding admissions with unrelated procedures, PTA cost $14,852 (SD $14,550) and bypass $14,288 (SD $7998) (no significant difference). Excluding additional unrelated procedures and related vascular procedures, PTA cost $8019 (SD
$5753) and bypass $13,439 (SD $6791) (p = 0.0001). With these exclusions and stratifying by indication, the mean hospital costs for PTA were significantly lower than those for bypass surgery for patients with claudication (p = 0.0001). The difference in costs between PTA and bypass surgery for patients treated for critical ischemia was of borderline significance (p = 0.08). No significant differences could be demonstrated for admissions for multiple revascularization procedures. Bypass surgery and PTA were performed in 42 cases; cost without thrombolysis was $21,244 (SD $15,529) and with thrombolysis $30,639 (SD $19,967). Admissions associated with an additional procedure for treatment of a complication or failure cost on average $46,245 (SD $23,340; n = 6) for PTA and $25,010 (SD $17,865; n = 23) for bypass (p = 0.02). Note that these results are subject to bias because the groups were determined retrospectively. Furthermore, the groups were too small to stratify meaningfully: five of the six PTA admissions and 19 of the 23 surgical admissions were for critical ischemia. Mean hospital costs and length of stay were highly correlated (R2 = 0.89; P = 0.0001). Excluding additional unrelated and related vascular procedures, the mean length of
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Hunink, Cullen, and Donaldson 637
Table IV. Incremental mean hospital costs and length of stay per admission determined with multiple regression for various factors for femoropopliteal revascularization including all admissions (n = 337) Factor* Bypass vs PTA Additional unrelated procedures:j: Additional related vascular procedures§ Debridement or amputation
Incremental mean cost and SE (US. 1990 dollars) (p valuet) 5,038 28,137 9,003 24,766
± 1,817 2,881 ± 1,868 ± 2,241
±
Incremental length of stay and SE (days) (p valuet) 6.3 20.6 6.0 24.0
(0.006) (0.0001) (0.0001) (0.0001)
± 1.8 (0.0004) ± 2.8 (0.0001) ± 1.8 (0.001) ± 2.2 (0.0001)
*Adjusted for the primary procedure performed, additional unrelated procedures, additional related vascular procedures, and debridement or amputation. The intercepts for the models were $5964 (SE $1767) for costs and 2.6 (SE 1.7) days for length of stay. The R2 was 0.47 for the cost model and 0.41 for the length of stay. tWald test for significance in multiple regression model. §Additional bypass, additional angioplasry, and thrombolysis. :j:Coronary artery bypass grafting, percutaneous heart valvuloplasty, carotid endarterectomy, abdominal aortic aneurysm repair, and other major surgery (see footnote Table III).
Table V. Components of the mean hospital costs per admission for femoropopliteal PTA and bypass* Mean cost in 1990 US. dollars (% of total cost) Critical ischemia
Claudication Component Procedural costs Diagnostic angiography/interventional radiology Operating room and anesthesia Hotel costs Routine room and board Intermediate/intensive care Supportive Diagnostic radiology (other than angiography) Clinical laboratory servicest Patient laboratory services:j: Pharmacy and blood bank§ Miscellaneous otherll Total
Bypass (n = 96)
PTA (n = 14)
(n
5,008 (81) o (0)
2,340 (20) 3,800 (33)
4,358 (38) 283 (3)
2,120 (14) 4,325 (29)
814 (13) o (0)
4,077 (35) 144 (1)
3,694 (33) 428 (4)
5,575 (37) 890 (6)
PTA (n = 25)
32 87 97 101 13 6,152
«1) (1) (2) (2) «1)
144 262 194 482 136 11,582
(1) (2) (2) (4) (1)
93 434 216 1,497 351 11,353
(1) (4) (2) (13) (3)
Bypass = 110)
243 485 293 799 328 15,059
(2) (3) (2) (5) (2)
*Excluding admissions associated with additional major procedures (additional bypass, additional angioplasty, thrombolysis, coronary artery bypass grafting, percutaneous heart valvuloplasty, carotid endarterectomy, abdominal aortic aneurysm repair, and other major surgery [see footnote Table III». Physicians' professional fees are excluded from the analysis. tlncludes chemistry, hematology, and microbiology. :j:lncludes noninvasive testing and electrocardiography. §Includes medications, intravenous solutions, and transfusions. IIlncludes inpatient rehabilitation, hemodialysis, and respiratory therapy.
stay was significandy different for PTA compared with bypass (4.2 vs 11.3 days; p = 0.0001). For patients with claudication the mean length of stay was significandy lower for PTA than for bypass (1.8 vs 9.3 days; p = 0.0001). For admissions for critical ischemia the difference in length of stay was of borderline significance (8.6 vs 13.0 days;p = 0.05). With multiple linear regression the incremental mean hospital costs and length of stay depending on the presence of various factors were determined for all admissions (Table IV). The significant covariates in
predicting mean hospital cost were the primary procedure, additional unrelated procedures, additional related vascular procedures, and whether debridement or amputation was performed during the same admission. Although a significant difference in indication and the prevalence of diabetes existed between patients treated with bypass versus PTA, neither was significant in predicting costs in the multiple regression analysis adjusting for the significant factors. This is probably because the effects of both indication and diabetes mellitus are reflected by
638 Hunink, Cullen, and Donaldson
whether debridement or amputation is performed. Mean costs and length of stay were influenced significantly by the outcome of morbidity or death, which increased hospital costs per admission by $13,065 (SE $1918;p = 0.0001) and length of stay by 11.1 days (SE 1.9;p = 0.0001). With adjustment for the primary procedure, additional related vascular procedures, additional unrelated procedures, debridement or amputation, and morbidity/mortality, the incremental cost of 1 day in the hospital was $939 (SE $24;p = 0.0001). Excluding admissions with additional related vascular or unrelated procedures, analysis of the cost components (Table V) demonstrated that for patients treated for claudication the procedural costs (i.e., diagnostic angiography, interventional radiology, operating room, and anesthesia) constituted the major proportion of the total costs (81 % for PTA and 53% for bypass). On the other hand, for patients treated for critical ischemia, the procedural costs were the same proportion as hotel costs (i.e., routine room and board and intensive/intermediate care), each constituting approximately 40% of the total cost irrespective of the procedure. Supportive costs were less than 25% of the total costs irrespective of procedure and indication. The procedural costs were similar for PTA and bypass; however, hotel costs were lower for PTA. Multiple regression analysis of the hospital costs for PTA over time, with adjustment for the significant covariates, demonstrated an increase of $1269 (SE $731) per year (p = 0.08) because of an increase in the costs for angiography and interventional radiology (Fig. 1). In contrast, analysis of the hospital costs for bypass over time demonstrated a nonsignificant decrease of $369 (SE $313) per year (p = 0.24) (Fig. 2). Multiple regression analysis of the mean length of stay over time, with adjustment for the significant covariates, demonstrated no change for PTA and a decrease of 1.1 day per year (p = 0.0001) for bypass.
DISCUSSION Table I reviews previously reported cost and charge data for PTA and bypass performed for peripheral arterial disease. The highest figures are charges reported by Wolf and McLean. ls However, their data are biased because of a long average hospital stay of 8.5 days for PTA and 26.8 days for bypass and, as they state, "skewed by a few patients with very long hospital stays and hence large bills." The reported costs of bypass and PTA in the United Kingdom are substantially lower than those in the United States. S,IS.2I Caution must be exercised in
JOURNAL OF VASCULAR SURGERY April 1994
interpreting these figures because the studies from the United Kingdom l7,21 enumerate actual costs, whereas those from the United States S,IS,16,18-20 present charges. Comparison of our cost estimates with previously published figures from the United States is hampered by the same problem. In general, charges are not a good approximation of costs. 22 For example, at the Brigham and Women's Hospital the ratio of costs to charges ranges from 0.75 to 1.0 for routine room and board, is generally larger than 1.0 for intermediate and intensive care, is approximately 0.40 for operating room services, and is close to 1.0 for angiography. Rather than evaluate charges, we evaluated costs by a method that estimates costs relative to charges per service rendered. Overall, charges exceeded costs by 20% to 30% for admissions for PTA and 50% for bypass. A comparison of nonrandomized patients who have undergone PTA versus bypass inherently brings with it the question whether the groups are comparable. In this study PTA was performed for less severe disease, which in the nonstratified, nonadjusted analysis may bias the costs for PTA toward lower values. On the other hand, admissions for PTA were more commonly associated with additional bypass and thrombolysis, biasing the costs upward. To identify whether differences in the PTA and surgical groups translated into predictable cost differences, the analysis was performed stratified by indication and additional procedures, and a multiple regression analysis was performed. In this analysis lesion severity was not significant in predicting costs, probably because the effect of lesion severity was reflected in other variables. Long lesions (> 5 cm), multiple lesions, and nonfocal occlusions may increase the costs of PTA, but these types of lesions in the femoropopliteallocation are currently not generally considered amenable to PTA. Although lesion severity may influence the costs of PTA, it is difficult to conceive how lesion severity (independently) will impact on the costs of bypass other than through variables such as indication, additional procedures, debridement, and amputation. Eight to 10 years ago, the costs of PTA were 19% to 34% of the costs of bypass (Table I), suggesting that cost savings might be possible if PTA was deemed effective. S,15-I7 In contrast, this study found that PTA currently costs on average 60% of the cost of surgery, a far less favorable ratio. The average ratio of 60% is partly a reflection of the significant difference in indication between the PTA and surgical groups. For patients treated for disabling claudication, the cost advantage of PTA over bypass was
JOURNAL OF VASCULAR SURGERY Volume 19, Number 4
Hunink, Cullen, and Donaldson 639
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significant: the cost of PTA is 53% that of a graft. For patients with critical ischemia, the difference in costs was of borderline significance, PTA costing 75% that of surgery. We attempted to explain why the ratio of PTA to that of bypass increased during the past 10 years. Analysis of the costs of PTA versus bypass suggested that the costs of PTA increased $1270 per year, whereas the costs of bypass decreased approximately $370 per year. Analysis of the cost compo-
nents suggested that for PTA the increase in cost was the result of an increase in cost of the actual procedure. A possible reason for the increasing costs of PTA could be the refinement of catheters and guide wires used during PTA or the use of more expensive (low-osmolar) contrast agents. For bypass, operating room expenses seemed to be more or less constant during the study period, the cost for diagnostic angiography increased, and hotel costs
640 Hunink, Cullen, and Donaldson
decreased. The latter observation agrees with the significantly decreased length of stay for bypass. This suggests that any increase in procedural or supportive costs for bypass was compensated by the decrease in hotel costs. For both bypass and PTA, hospital costs were dependent on the indication for the procedure. This finding is supported by Gupta and Veith, 20 who observed the same indication-dependent discrepancy in hospital charges for vascular surgery. In patients treated for critical ischemia, the difference in mean hospital costs of PTA and bypass was of borderline significance, suggesting that the costs of a hospital admission for revascularization for critical ischemia are determined mainly by adjuvant treatment and the cost of the actual procedure performed is a small proportion of the total costs. This hypothesis is supported by this study through (1) the stratified analysis, which demonstrated a significant difference for patients with ischemia if neither debridement nor amputation was performed; (2) the multiple regression analysis, which demonstrated that performing ulcer debridement or amputation was significant in predicting costs; and (3) the analysis of cost components, which demonstrated that the costs for the actual procedure were a smaller fraction of the total cost for patients with critical ischemia than for patients with claudication. In addition to indication, mean hospital costs for revascularization also correlated with complications and length of stay. Because the latter are outcomes and not independent variables, they were not included in the baseline regression analysis, because for meaningful decision making predictions of cost should be based on information available before the choice of procedure. However, including these as independent variables and with adjustment for the significant covariates, the incremental cost associated with complications and an extra day in the hospital were approximately $13,000 and $1000jday, respectively. In conclusion, the observation that PTA is not as inexpensive relative to bypass as it previously seemed to be, together with current reports of the efficacy of PTA based on strict outcome criteria and reporting standards,29 may necessitate a reassessment of the indications for PTA. A cost-effectiveness analysis comparing PTA with medical treatment and bypass may help resolve this issue. 5,7,11,22 Such an analysis needs to be stratified for varying severity of disease, at the least distinguishing patients by indication, because revascularization performed for critical ischemia has a higher risk, yields lower long-term
JOURNAL OF VASCULAR SURGERY April 1994
patency, and costs more than revascularization performed for claudication. Furthermore, whether the optimal treatment for claudication is intervention or conservative treatment requires clarification. However, some variables remain to be elucidated before a comprehensive reassessment and cost-effectiveness analysis of the treatment of peripheral arterial disease are feasible, including the long-term results of medical or conservative treatment and the improvement in quality of life after various forms of treatment. We acknowledge the assistance of Julie Lombara in retrieving clinical information on study patients. REFERENCES 1. Becker GJ, Katzen BT, DaKe MD. Noncoronary angioplasty. Radiology 1989;170:921-40. 2. Donaldson MC, Mannick JA, Whittemore AD. Femoraldistal bypass with in situ greater saphenous vein. Ann Surg 1991;213:457-65. 3. Johnston KW, Rae M, Hogg-Johnston SA, et al. Five-year results of a prospective study of percutaneous transluminal angioplasty. Ann Surg 1987;206:403-13. 4. Veith FJ, Gupta SK, W~ngerter KR, et al. Changing arteriosclerotic disease patterns and management strategies in lower-limb-threatening ischemia. Ann Surg 1990;212:40214. 5. Doubilet P, Abrams HL. The cost of underutilization: percutaneous transluminal angioplasty for peripheral vascular disease. N Engl J Med 1984;310:95-102. 6. Tunis SR, Bass EB, Steinberg EP. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease. N Engl J Med 1991;325:556-62. 7. Coffman JD. Intermittent claudication: be conservative. N Engl J Med 1991;325:577-8. 8. Pentecost MJ. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease [letter;comment]. N Engl J Med 1992;326:413. 9. Veith FJ, Peder BA, Bakal CWo Letter to the editor in response to Tunis SR, Bass EB, Steinberg EP. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease [letter]. N Engl J Med 1992;326:413-4. 10. Osterman FA Jr. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease [letter; comment]. N Engl J Med 1992;326:414. 11. Hunink MGM, Meyerovitz MF. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease [letter]. N Engl J Med 1992;326: 414. 12. Clugston RA, Eisenhauer AC, Matthews R V. The use of angioplasty, bypass surgery, and amputation in the management of peripheral vascular disease [letter]. N Engl J Med 1992;326:415. 13. Becker GJ, Ferguson JG, Bakal CW, et al. Angioplasty, bypass surgery, and amputation for lower extremity peripheral arterial disease in Maryland: a closer look. Radiology 1993; 186:635-8. 14. McNeil B. The changing financial picture in health: impact on radiology and the use of new technologies. Eugene P.
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Submitred April 1, 1993; accepted June 12, 1993.