The effects of patient characteristics on ambulatory test ordering

Sot. Sci. Med. Vol. 21, No. 10, pp. 1071-1075, Printed in Great Britain. All rights reserved

1985 Copyright

THE EFFECTS OFPATIENTCHARACTERISTICS AMBULATORYTESTORDERING

0277-9536185 $3.00 + 0.00 ‘~c 1985 Pergamon Press Ltd

0~

ARNOLD M. EPSTEINand BARBARAJ. MCNEIL Department of Medicine, Division of General Medicine, the Brigham and Women’s Hospital, Institute for Health Research, a joint program of the Harvard Community Health Plan and Harvard University; and Departments of Radiology and Preventive Medicine and Clinical Epidemiology, Harvard Medical School, Boston, Mass., U.S.A. Abstract-To investigate the relationship of patient characteristics and the use of ambulatory testing services, we examined patterns of test use for 351 patients with chronic uncomplicated hypertension, cared for by 30 private practice internists. We studied the use of visits and diagnostic tests in relation to patients’ sex, marital status, obesity, employment status, occupational class, insurance coverage and severity of illness in terms of age, extent of blood pressure elevation and number of medications used in treatment. Testing services accounted for 63% of the total expenditure for testing and physician services. Females and patients with greater severity of disease had higher visit rates, and age was significantly related to increased test use. Marital status, obesity and socioeconomic characteristics were not strongly associated with patterns of testing. Our results suggest that patterns of testing for hypertensive patients are related to severity of illness in terms of age but not to patients’ socioeconomic characteristics.

RCutn&-Pour Ctudier la relation qui existe entre les caracteristiques des patients et le recours aux tests diagnostiques en dehors de I’hopital, nous avons examine la consommation de tests par 351 patients atteints d’hypertension chronique sans complication et soignes par 30 intemes en pratique privcte. Nous avons mis en rapport le recours aux visites et aux tests avec le sexe, le statut marital, fob&it& le type d’occupation, I’importance de la couverture d’assurance et la s&&rite de la maladie exprimte en terme d’age, de niveau de la pression sanguine et du nombre de midicaments utilises pour le traitement. La consommation de tests reprtsente 63% des dtpenses totales pour les visites et les tests. Les femmes et les patients atteints plus serieusement ont un taux de visite chez le midecin plus eleve et Page influence

de facon significative le recours aux tests. Le statut marital, l’obesitk et les caracttristiques socioCconomiques ne sont pas fortement corrtks avec la consommation de tests. Nos resultats suggtrent que la consommation de tests lies a l’hypertension depend de la skviriti: de la maladie exprimee par I’ige mais pas des caracttristiques socio-tconomiques des patients.

INTRODUCTION Over 10 years ago, Freeborn [l], Schroeder [2] and their associates began a series of studies on factors influencing the utilization of diagnostic tests. Since then, several investigators have studied factors related to the physician or the setting in which he/she. practices which lead to increased diagnostic testing [3]. These studies have suggested, for example, that physicians who are younger [4-61, who are trained in academic centers [7], who practice in large groups [8] or who have on-site laboratory services available

This work has been supported in part by grants from the John Hartford Foundation and from the Welicome Foundation and the Commonwealth Fund and by the Institute for Health Research, a joint program of the Harvard Community Health Plan and Harvard University. Dr Epstein was a Medical Foundation Fellow, 1982-1984, when this work was initiated. Dr Epstein is currently a Henry J. Kaiser Family Foundation Faculty Scholar in General Internal Medicine. Send all correspondence to: Dr A. Epstein, The Institute for Health Research, Harvard School of Public Health. 677 Huntington Avenue, Boston, MA 02115, U.S.A.

[S, 6,9] tend to use diagnostic services for ambulatory patients more extensively than do their colleagues without these characteristics. Despite current interest in promoting appropriate ancillary test usage, there has been little research on patient related characteristics that might be associated with particular patterns of diagnostic testing. This is an important area to investigate since previous studies have suggested that patient factors are associated with particular patterns of hospital utilization [lO-121 and ambulatory visits [13-161. In this investigation we have performed a pilot study to evaluate the role of patient factors in ambulatory diagnostic testing. We were interested in two types of associations: (1) the relationship between socioeconomic status and ambulatory test use; and (2) the relationship between indices of severity of illness and rates for ambulatory visits and testing. In both cases we were interested in these relationships as they might affect the quality of care or cost of care. We studied patients with ‘uncomplicated hypertension’ because of its high prevalence and because of the ease with which its severity can be determined. To increase generalizability we examined care for patients seen by private office internists.

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ARNOLD M. EPSTEINand BARBARA J. MCNEIL METHODS

Data collection

We first identified physicians by choosing six community hospitals in the Boston area. All doctors who had admission privileges at those hospitals and were board certified in internal medicine but without subspecialty boards were invited to participate in the study. Thirty-nine physicians met these criteria and 30 (77%) agreed to participate in a study of ambulatory test use. All these physicians practised full-time in private office, fee-for-service settings. Of the 9 physicians who declined participation, 4 suggested that potential difficulties of coordination with our research assistants and the intrusion of strange personnel in their offices prompted their decision. The other non-participants gave no clear reason for their decision. Further details of their practice settings are described in a previous publication [8]. Patients were selected from an on-site chart review. To standardize the case-mix we required that all patients have medical insurance, be older than 16 years of age and have uncomplicated hypertension diagnosed prior to 1 July 1977. We classified patients as having hypertension when the diagnosis of hypertension was indicated in the physician’s office notes and the patient was treated with a diuretic or other antihypertensive agent. We defined ‘uncomplicated’ hypertension as hypertension occurring in a patient with no history of complications, other chronic disease, previous myocardial infarction or any acute cardiac problems. In order to ensure that we had reasonably complete data on all patients, those selected had to demonstrate evidence of continuing care with at least two office visits during a 2-year index period, 1 January 1978-31 December 1979, or a single office visit during the last 6 months of that index period. For each physician, we collected data on up to 15 patients who met the above criteria. For all patients, we abstracted their outpatient records to obtain demographic and diagnostic data, information about employment status and if employed, occupation, information about insurance coverage, weight, current antihypertensive medications, the highest blood pressure reading recorded during the index period, the number of office visits and the number and types of all radiographic and laboratory tests performed between 1 January 1978 and 31 December 1979. Tests analyzed in the study included only those ordered by the patient’s primary physician or a covering doctor or nurse practitioner. Data analysis

The purpose of our analysis was to examine the effects of patients’ demographic and socioeconomic characteristics and their severity of illness on the use of ambulatory services, especially testing. The demographic and socioeconomic characteristics we examined included sex, marital status, obesity, insurance coverage, employment status and occupation. To examine obesity we compared groups of patients who weighed more than 220 lb if male and 195 lb if female to those who weighed less. We chose these levels because males 6’2” or less who weighed more than 220 lb and females 6’ or less who weighed more than 195 lb would be at least 30% overweight [17].

Patients’ occupations were classified in relation to a standard schema [ 181 (Professional, Employers and managers, Intermediate nonmanual, Skilled manual, Semi-skilled manual and Unskilled manual). Indices of disease severity included age, the number of medications used in treatment and the level of blood pressure elevation. We examined seven outcome measures of ambulatory utilization: average number of visits per patient per year (visits/pt/yr); average testing charges per patient per year (testing charges/pt/yr); average cost of care per patient per year (cost/pt/yr); and the average use per patient per year of four individual tests-electrocardiograms (EKGs/pt/yr), chest radiographs (CXRs/pt/yr), blood counts (CBCs/pt/yr) and urinalyses (UAs/pt/yr). We chose these four tests because they are used commonly and ordered individually rather than in panels (e.g. SMA-12). Hence there was no distortion by differential availability in different sites. In the calculations, charges for tests and office visits were based on the 1981 Blue Shield customary reimbursement levels in Massachusetts. In the first part of the analysis, we used two-tailed t-tests, one-way analysis of variance and linear regression to examine whether any of the patients’ demographic, socioeconomic or disease characteristics were associated with increased utilization in terms of visits/pt/yr, testing charges/pt/yr or cost/pt/yr. Then to ensure that our positive findings were independent, we included the characteristics for which an effect was demonstrated as independent variables in a multiple regression analysis. As part of that analysis, we also included group size as a binary [large group (2 5 members) vs small group and solo group practice] independent variable. We did this to eliminate possible confounding since findings in our previous research have suggested that practice in a large group setting is associated with the increased use of diagnostic tests 181.x2 for trend analyses were used to examine use of individual tests after the patients were divided into those who received none of those services and those who received one or more of them. Throughout the analyses we used the patient (N = 351) as the unit of evaluation since the study was designed to examine the relationship of patients’ characteristics on utilization by the patient. RESULTS

The study population consisted of 351 patients 11.7 &-3.7 patients physician) (mean per (mean f SD). Table 1 shows the demographic and socioeconomic characteristics of the patients in the study population. Average age was 58.0 f 13.0 years (mean f SD) and 62% were female. Overall, the average cost of visits and tests was $134 per patient per year. Sixty-three percent of these costs were related to testing. During the two year period 92% of patients had at least one diagnostic test. In general, costs for testing exceeded the costs for visits; for only 40% of patients did the reverse situation hold. Socio-demographic

characteristics

Table 2 displays the relationship of patients’ sociodemographic characteristics (other than age) and

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Patient characteristics and testing Table Demographic characteristics

I. Characteristics

and their ambulatory utilization. We compared the 290 patients who had at least some private insurance coverage with the 61 patients without any private coverage and found no significant differences in utilization. Likewise, neither employment status nor occupational classification was predictive of increased or decreased utilization.

of patients

and socioeconomic Number

of patients

58.0 t I3 62”,6

Age (mean years k SD) Sex (T/, female) Marital status Single Married Divorced Widowed Unknown Weight (mean lb 5 SD) Employment status Employed Unemployed Retired Unknown Occupational class 1. Professional 2. Employers and managers 3. Intermediate nonmanual 4. Skilled manual 5. Semi-skilled manual 6. Unskilled manual Unknown Patient insurance coverage Blue Cross/Blue Shield (BCIBS) Commercial Medicare Medicaid Medicare and BCiBS or Commercial

I6 179 I6 33 107 167535

Severity

I15 18 64 IS4 22 37 47 33 29 20 163

DISCUSSION

146 85 51 IO 59

This investigation was a pilot study aimed at quantitating the effect of several factors that might influence ambulatory care practices for a group of patients with a single chronic diseaseuncomplicated hypertension. We studied factors related to the socioeconomic status of the patient as well as to the severity of their illness. Our results confirm, in part, studies by others and, in addition, provide new information in a number of areas. In particular, they suggest that at least in this group of patients quality of care does not appear to be influenced by socioeconomic factors. In terms of the effects of sex, our data confirmed the fact that utilization of ambulatory visits is higher among women than among men [ 15, 191; however, this effect did not extend to increased utilization of ambulatory tests. In terms of socioeconomic status, we found no definite trend toward increased testing among those with private insurance vs those without. Similarly we found no effect of higher occupational class on test usage. These results are different from those of two previous investigators, who after controlling for health status, found a decreased ambulatory visit rate among the poor [13, 141. It might

utilization. Gender was the major determinant of usage. For example, annual visit rates (mean + SD) for female patients (2.7 + 2.1) were statistically higher than those for males (2.2 f 1.5); however, use of tests was similar, except for the use of blood counts which showed a trend toward higher use by females. There was no significant difference in visits or testing among groups of patients in relation to their marital status. Similarly, there was no difference in utilization between patients who were or were not categorized as obese. Multivariate analyses confirmed that the effect we found for gender on visit rates was independent of group size and other predictive patient characteristics discussed below. Socioeconomic

characteristics

Table 3 displays information about the relationship of patients’ socioeconomic characteristics

Table 2. Pattents’ Visits: PtiYr Sex Male (135) Female (216) Marital status Single (16) Married (179) Divorced ( 16) Widowed (33) Obese6 No (296) Yes (36)

2.2 _+ 1.5: 2.7 + 2.1 3.4 2.5 2.2 2.8

& 3.0 + 1.9 * 1.0 2 2.4

2.5 i 1.9 2.3 f 1.9

socio-demographic Testing charges, pt/yr+

of illness

All three measures of severity-age, number of medications and extent of blood pressure elevationwere associated with higher visit rates (Table 4). Age also was associated with higher testing charges and a higher total cost of care, whereas the number of medications and the extent of blood pressure elevation were not associated with increased testing. In multivariate analysis, we found that the effects for all three measures of severity remained statistically significant except for borderline significance for the effect of medications on visits (0.05 < P < 0.10).

characteristics cost; pt/yr+

in relation

to utilization*

EKGs/ PtlYr

CXRs,’ Pt/Yr

CBCs/

ptiv

UAs/ PtiYr

77 * 100 88 * 93

122 i 108 l42? III

0.45 i 0.50 0.43 * 0.50

0.29 f 0.47 0.28 i 0.38

0.47 f 0.53 0.66 + 0.73

0.45 k 0.58 0.39 f 0.51

78 k91 87 k 99 68 I86 IlO+ 127

146 + 135 l37i 113 112296 167 i 143

0.32 0.49 0.50 0.50

0.22 0.34 0.25 0.24

0.84 0.61 0.59 0.66

0.37 0.44 0.44 0.42

84 ? 97 93 * 93

134* II2 148 + 112

0.45 f 0.55 0.38 t 0.40

*Numbers in parentheses refer to number of patients. tin dollars (mean + SD). ZDifference significant at P < 0.05. @Males with weight above 220 lb; females with weight

above

195 lb.

i + * i

0.31 0.59 0.37 0.56

? 0.26 It: 0.47 f 0.41 it 0.34

0.28 i 0.42 0.28 + 0.35

k + + f

0.95 0.70 0.65 0.85

0.60 i 0.68 0.51 + 0.66

f + i +

0.65 0.55 0.60 0.45

0.44 + 0.55 0.33 f 0.45

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M.

ARNOLD Table 3. Patients’

socioeconomic

Visits/ PtlYr Method of payment Private insurance(BC/BS, Commercial, Medicare and private coverage) (290) No private insurance (Medicare alone. Medicaid) (61) Employment status Employed ( 115) Unemployed (18) Retired (64) Occupational class 1. Professional (22) 2. Employers and managers (37) 3. Intermediate nonmanual (47) 4. Skilled manual (33) 5. Semi-skilled manual (29) 6. Unskilled manual (20)

characteristics

Testing charges/ ptiyrt

to utilization*

EKGs/ ptiyr

CXRs, pt:yr

CBCs/ PtiYr

UAW PtiYr

84 ? 89

135 * 106

0.43kO.50

0.28kO.36

0.5610.62

0.41 +0.50

2.4 + 1.6

82 + 125

131 f 129

0.45 f0.68

0.28~0.60

0.68+0.85

0.42+0.69

2.3 + 1.4 2.9 f 2.1 2.7 f 2.1

75 * 101 63 i 54 88 * 107

122 * 105 I21 k 82 141 + 123

0.42 i_ 0.57 0.31 20.35 0.43 i 0.59

0.28 k 0.49 0.17+0.25 0.29 f 0.42

0.46 it 0.56 0.5720.80 0.68 k 0.74

0.40 k 0.59 0.22kO.36 0.39 + 0.46

88 f 73 90 f 103 67k51 106 t 155 77 & 85 56 f 55

149* 113 136 i 108 114i.59 156 + 157 128 f 98 97 * 63

0.53 0.46 0.36 0.61 0.42 0.20

0.28 k 0.30 + 0.23 + 0.44+ 0.28 ? 0.30 k

0.53 0.50 0.53 0.61 0.48 0.48

0.31 0.47 0.40 0.55 0.32 0.35

k + f f + +

3.6 1.4 1.4 I .8 1.5 1.0

k 0.45 i 0.50 -f. 0.43 + 0.73 + 0.60 k 0.25

0.34 0.38 0.33 0.75 0.35 0.30

k 0.42 f 0.44 + 0.48 50.80 i 0.58 f 0.64

I f f + k +

0.37 0.50 0.40 0.65 0.47 0.38

of patients

Table 4. Patlents’

Age 21-45 (63) 46-60 (125) 6lf (150) Number of medications 1 (204) 2 (120) >3 (27) Diastolic blood pressure 80-89 (95) 9&99 (97) IO&l09 (85) I I& (51)

in relation

cost/ pt:yrt

have been assumed that such a decreased rate would be accompanied by decreased testing as well. Our data on the effects of severity of illness indicate that all three indices of disease severity-age, number of antihypertensive medications used in treatment and extent of blood pressure elevation-are related to visit rates. Only age, however, was associated with increased testing. We suspect that the lack of relationship for the other measures of severity may reflect the fact that there is no clear relationship of testing to appropriate blood pressure management. In other clinical situations in which the results of tests may have important implications for management (e.g. an abnormal urine sugar or glycosylated hemoglobin for patients with diabetes mellitus or an abnormal intravenous pyelogram *for patients with newly diagnosed hypertension), indices of severity may be more strongly associated with test use. Our results might be compared to those of a recent study by Hartley et al. [20] that examined the influence of patient characteristics on test ordering in

Visits/ PtlYr

BARBARA J. MCNEIL

2.5 * 1.9

3.1 2.3 2.4 2.6 2.6 2.1

‘Numbers in parentheses refer to number IIn dollars (mean + SD).

and

EPSTEIN

Testing charges/ pt/yr+

severity

a series of general practices in the greater London area. After controlling for the effects of the patients’ diagnosis, doctor and age, social class explained less than one percent of the interpatient variation in test use. Although the effects of socioeconomic status were weak, Hartley found that significantly fewer tests per consultation were ordered for patients in lower socioeconomic classes than for patients in the highest two social classes; however, since visit rates were also significantly higher among the lower socioeconomic classes, there was overall a significantly higher use of tests for those patients. Our findings on the overall use of tests are also of interest. In our study, the estimated cost for testing was 63% of the estimated cost for testing and physician services. These estimates, of course, only provide a rough gauge since they are very sensitive to the relative prices attached to visits and tests. The scale we used-Massachusetts customary reimbursement rates-cannot be completely generalized. The relative utilization of tests in our study is substantially higher

of illness cost/ ptiyrt

m relation

to utilization*

EKG/ PtiYr

CXRsi PtiYr

CBCs/ Pt/Yr

UAs/ PtiYr

2.2 & 1.3$ 2.3 + 1.5 2.7 + 2.2

65 f 67: 80 k 87 95*113

109 * 799 126?99 149 * 130

0.38 k 0.44 0.43 i 0.48 0.46 f 0.61

0.26 f 0.35 0.25 * 0.34 0.3 I + 0.50

0.40 i 0.44 0.59 i 0.62 0.65 i 0.76

0.39 t 0.52 0.37 * 0.51 0.44 f 0.58

2.3 f I.79 2.7 F 2.0 3.4 * 2.5

85 k 105 87 k 86 63 f 60

131 * 115 140 i 209 131 f 83

0.46 + OS7 0.41 * 0.49 0.41 f 0.40

0.29 + 0.46 0.26 + 0.34 0.32 k 0.35

0.63 ? 0.68 0.52 k 0.62 0.52 k 0.76

0.37 + 0.52 0.47 f 0.58 0.46 +_0.49

75 93 83 66

114191 144 * 137 136 f 103 126+_92

0.35 0.56 0.38 0.39

0.23 0.33 0.30 0.25

0.61 0.70 0.54 0.37

0.36 * 0.44 0.44 + 0.63 0.46 k 0.55 0.3 I k 0.46

2.0 2.6 2.7 3.0

f I .2g i 2.3 k 1.7 * 2.2

*Numbers in parentheses refer to number tin dollars (mean ? SD). tDitTerence significant at P < 0.05. $Difference significant at P c 0.01.

& 87 * I20 f 87 + 65

of patients

+_0.42 & 0.65 f 0.46 * 0.53

t * * i

0.33 0.53 0.38 0.32

* ? f f

0.66 0.78 0.66 0.48

Patient characteristics than the 2535% estimated by Scitovsky [21]; but her calculations were for all patients, rather than those with a chronic disease. While diagnostic testing is always an important component of ambulatory care, our results underscore the extraordinary importance testing plays for particular patient groups, and they suggest a special need for investigations to determine

optimal patterns of utilization in clinical instances such as these. For a number of reasons, we believe our results should be considered as preliminary. First of all, we used a retrospective format, obtaining data from office charts. Since information on patients’ height was not generally available we had to use a proxy measure for obesity and combine patients of normal and below-normal weight. Also we had no employment information or occupational classification for a substantial portion of our patient population. Eighty percent of the patients for whom we lacked occupational classification were women and we presume that many of these patients were housewives, not formally employed. However, we often did not have available a husband’s occupation which would have allowed us to make an accurate occupational classification. Also important, all of our patients were medically insured and under the continuing care of a medical physician. These are social characteristics which may themselves be very restrictive. Finally, our results reflect the care of hypertensive patients, treated by internists. As we discussed above, we must question whether the findings can be generalized to patients in other clinical situations or cared for by different types of physicians. Our findings suggest that diagnostic testing is a major component of the costs of ambulatory care for patients with chronic hypertension. In this group of patients, controlled for disease, patients’ socioeconomic characteristics including occupational class do not appear to be strongly related to utilization. Other patient characteristics related to socioeconomic status such as patients’ income may be related to test use and deserve study. However, our results suggest that for patients with a chronic disease, socioeconomic characteristics do not have a large influence on the ambulatory use of diagnostic testing. Acknowledgement-We are grateful to the thirty anonymous private practitioners who graciously allowed us to monitor their practice patterns. REFERENCES 1.

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