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March CME
CONTINUING MEDICAL EDUCATION PROGRAM JACS CME-1 FEATURED ARTICLES, VOLUME 196, MARCH 2003 A comparison of diet and exercise therapy versus laparoscopic Roux-en-Y gastric bypass surgery for morbid obesity: a decision analysis model Patterson EJ, Urback DR, Swanstro¨m LL J Am Coll Surg 2003;196:379–384 A cost-effectiveness analysis of intraoperative cholangiography in the prevention of bile duct injury during laparoscopic cholecystectomy Flum DR, Flowers C, Veenstra DL J Am Coll Surg 2003;196:385–393 Objectives: After reading the featured articles published in this issue of the Journal of the American College of Surgeons (JACS) participants in the JACS CME program should be able to demonstrate increased understanding of the material specific to the article featured and be able to apply relevant information to clinical practice. Objectives are stated at the beginning of each featured article; the questions follow with 5 response choices, and a critique discussing the objective. The American College of Surgeons is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor continuing medical edu-cation for physicians. The JACS CME program fulfills the ACCME essentials. You can earn two CME credits using JACS CME Online, at http://jacscme.facs.org, or you can earn one CME credit if you submit this page by fax (see instructions in box below).
JACS CME Online provides four articles from each issue for two credits per month. The articles this month on JACS CME Online are: A comparison of diet and exercise therapy versus laparoscopic Roux-en-Y gastric Bypass surgery for morbid obesity: a decision analysis model. Patterson EJ, Urback DR, Swanstro¨m LL A cost-effectiveness analysis of intraoperative cholangiography in the prevention of bile duct injury during laparoscopic cholecystectomy. Flum DR, Flowers C, Veenstra DL The use of fresh frozen plasma after major hepatic resection for colorectal metastasis: is there a standard for transfusion? Martin RCG II, Jarnagin WR, Fong Y, et al. Effects of hospital volume on life expectancy after selected cancer operations in older adults: a decision analysis. Finlayson EVA, Birkmeyer JD
Earn 1 CME Credit by FAX Based on 2 articles in this issue (see next page), complete information below and fax to 312/202-5027 (Fax only, no mail submissions)
Earn Two CME Credits Online Log on to JACS CME Web site:
Name: ACS Fellow ID# Your fax number:
http://jacscme.facs.org Questions: Wendy Cowles Husser, MA, MPA Executive Editor, JACS 633 N Saint Clair Street, Chicago, IL 60611 312-202-5306 (ph) 312-202-5027 (fax) [email protected]
ANSWERS: Article 1 Article 2 Question 1 Question 1 Question 2 Question 2
© 2003 by the American College of Surgeons Published by Elsevier Science Inc.
501
ISSN 1072-7515/03/$21.00 PII S1072-7515(02)01805-7
502
Continuing Medical Education Program
A comparison of diet and exercise therapy versus laparoscopic Roux-en-Y gastric bypass surgery for morbid obesity: a decision analysis model Patterson EJ, Urback DR, Swanstro¨ m LL J Am Coll Surg 2003;196:379–384 Learning Objectives: To understand the role of bariatric surgery in the management of morbid obesity, and to understand the benefits and limitations of clinical decision analysis. Question 1 Persons with morbid obesity a) have a body-mass index greater than or equal to 40 kg/m2. b) should be offered bariatric surgery as the initial treatment. c) have a relative risk of death similar to persons with a normal weight. d) who have had a Roux-en-Y gastric bypass are usually not able to maintain a body-mass index less than 35 kg/m2 over the long term. e) are frequently able to achieve a body-mass index less than 35 kg/m2 without operation over the long term without surgery. Critique: Morbid obesity is defined as a body-mass index greater than or equal to 40 kg/m2. According to a National Institutes of Health Consensus Statement, patients judged by experienced clinicians to have a low probability of success with nonsurgical measures, as demonstrated, for example, by failures in established weight control programs or reluctance by the patient to enter such a program, might be considered for surgery. The risk of death from all causes increases over the range of moderate and severe obesity for both men and women at any age. Late followup of isolated gastric bypass has demonstrated that a body-mass index below 35 kg/m2 can be achieved by 93% of patients with obesity or morbid obesity, and by 57% of patients with “super-obesity” (those with an initial body-mass index of 50 kg/m2 or greater). Although physician-supervised, very low calorie diets might have dramatic shortterm success, most patients regain their lost weight within 1 year. A minority of obese patients treated with diet therapy, pharmacologic therapy, dietary counseling, or behavioral therapy are able to maintain substantial longterm weight loss. Question 2 In a clinical decision analysis
J Am Coll Surg
a) only two treatment alternatives can be compared in any one decision analysis model. b) the results of a decision model are unaffected by the estimates of the model parameters. c) a utility is a quantitative measure of the relative desirability of an outcome or health state. d) a valid estimate of the optimal treatment strategy can be determined even if there are no known data on the probabilities of chance events and the value of the outcomes. e) treatment alternatives can be compared with respect to effectiveness or with respect to cost, but not both. Critique: Decision analysis can be used to select the optimal treatment choice from two or more treatment alternatives. The results of a decision analysis are heavily influenced by the values assigned to the probabilities of chance events, and to the utility values assigned to the outcomes. Sensitivity analysis is a method of systematically varying the values of the variables included in the model, to determine the effect of uncertainty in the estimation of these variables on the results. The conclusions of a model are valid only to the extent that the underlying decision tree is correct, and the estimates of the probabilities of chance events and treatment outcomes are realistic. A utility is a quantitative measure of the relative desirability of an outcome or health state. The outcome to be optimized in a decision analysis model can be a measure of effectiveness, such as expected survival or quality-adjusted survival, cost, or a costeffectiveness ratio. A cost-effectiveness analysis of intraoperative cholangiography in the prevention of bile duct injury during laparoscopic cholecystectomy Flum DR, Flowers C, Veenstra DL J Am Coll Surg 2003;196:385–393 Learning Objectives: To evaluate the cost implications of routine cholangiography in reducing the rate of common bile duct injury during cholecystectomy and to appreciate the components of and variability involved with formal cost analytic techniques. Question 1 Cost analysis a) uses base-case estimates that are the lowest values identified in the literature. b) compares the cost per quality-adjusted life years but does not allow for comparisons to other interventions. c) is an exact science.
Vol. 196, No. 3, March 2003
d) must include sensitivity analyses to be complete. e) divides the costs of the intervention into the costs of the outcome. Critique: Cost analysis is part of a set of analytic techniques that uses estimates from varied sources to determine the cost components of a given outcome. The best estimates of the probability of related events and costs of each event and outcome are obtained and used in comparative base-case models to determine the cost per event. By including the amount of life years saved and measurements of the quality of that remaining life in the outcomes, simple cost analysis becomes cost-effectiveness analysis. The benefit of including qualityadjusted life years as an outcome measure is that qualityadjusted life years are easily comparable across interventions. Health policy analysts can then compare various interventions to determine relative merits using a common comparator. Cost, cost-efffectiveness, and decision analysis are not exact sciences. Rather, these techniques are a more formalized means to evaluate medical decision-making using the best available data and assumptions based on those data. These techniques are considered to be better than judgments made in dayto-day clinical practice about the “worth” of certain interventions because they explicitly identify transition probabilities and allow for scrutiny of these underlying assumptions. There are usually no statistical tests to confirm a cost analysis, but a complete cost analysis includes a sensitivity analysis. Sensitivity analysis demonstrates the impact of variation in all the parameters being measured and so helps to evaluate the integrity of the analysis. In a properly developed model, variation in probabilities along the range of possible values should not impact the overall conclusions of the cost analysis. Question 2 Regarding the cost of cholangiograms in preventing CBD injury: a) This study assumes from observational studies that more widespread use of an intraoperative cholangiogram will decrease the rate of CBD injury. b) The cost of buying a fluroscope should not be considered when performing cost analysis. c) Only the durable costs of the cholangiogram catheter are relevant to determining costs.
Continuing Medical Education Program
503
d) The cost of malpractice litigation related to bile duct injury should be included in this type of cost analysis. e) Cholangiogram is only cost effective when applied to high-risk patients. Critique: The rate of bile duct injury is so low (1:200– 1:350) that a prospective study to evaluate whether cholangiograms reduce the rate of CBD injury would require more than 26,000 patients. Because it is unlikely that such a study will be performed, to understand the role of cholangiograms we must extrapolate from large population-based studies that show nearly a doubling in the rate of CBD injury when no cholangiogram is performed. This extrapolation is problematic because retrospective, observational studies cannot be used to ascribe cause and effect. Because there might be important confounders (both measured and unmeasured) in observational studies, they should only be used to describe associations. When multiple observational studies point out the same effect and the same magnitude of effect and when that link is biologically plausible, the strength of evidence supporting causality grows. But by epidemiologic standards this still falls short of a cause-and-effect relationship and requires that an assumption be made. Regarding the specifics of this cost analysis, a complete analysis includes the material costs of the cholangiogram catheter, the capital costs of purchasing a fluoroscope, and the opportunity costs of occupied operating room personnel and space. Including all these components in a cost analysis indicates that cholangiogram is cost-effective when applied by all surgeons and on all patients. Legal costs associated with the outcome are not typically included in formal cost analysis because it is assumed that these costs are already incorporated into the cost averaging of health care. This study demonstrates that cholangiogram use was cost-effective for all patients and surgeons. The costeffectiveness of cholangiogram is greater when it is applied by high-risk surgeons (early experience with cholecystectomy) or among higher-risk patients (those with pancreatitis and other acute biliary disease). Unfortunately, predicting who will have a bile duct injury during cholecystectomy is problematic, and routine cholangiogram use might be the only reasonable approach from a public health perspective.
JACS CME Online provides four articles from each issue for two credits per month. The articles this month on JACS CME Online are: A comparison of diet and exercise therapy versus laparoscopic Roux-en-Y gastric Bypass surgery for morbid obesity: a decision analysis model. Patterson EJ, Urback DR, Swanstro¨m LL A cost-effectiveness analysis of intraoperative cholangiography in the prevention of bile duct injury during laparoscopic cholecystectomy. Flum DR, Flowers C, Veenstra DL The use of fresh frozen plasma after major hepatic resection for colorectal metastasis: is there a standard for transfusion? Martin RCG II, Jarnagin WR, Fong Y, et al. Effects of hospital volume on life expectancy after selected cancer operations in older adults: a decision analysis. Finlayson EVA, Birkmeyer JD
Earn 1 CME Credit by FAX Based on 2 articles in this issue (see next page), complete information below and fax to 312/202-5027 (Fax only, no mail submissions)
Earn Two CME Credits Online Log on to JACS CME Web site:
Name: ACS Fellow ID# Your fax number:
http://jacscme.facs.org Questions: Wendy Cowles Husser, MA, MPA Executive Editor, JACS 633 N Saint Clair Street, Chicago, IL 60611 312-202-5306 (ph) 312-202-5027 (fax) [email protected]
ANSWERS: Article 1 Article 2 Question 1 Question 1 Question 2 Question 2
© 2003 by the American College of Surgeons Published by Elsevier Science Inc.
501
ISSN 1072-7515/03/$21.00 PII S1072-7515(02)01805-7
502
Continuing Medical Education Program
A comparison of diet and exercise therapy versus laparoscopic Roux-en-Y gastric bypass surgery for morbid obesity: a decision analysis model Patterson EJ, Urback DR, Swanstro¨ m LL J Am Coll Surg 2003;196:379–384 Learning Objectives: To understand the role of bariatric surgery in the management of morbid obesity, and to understand the benefits and limitations of clinical decision analysis. Question 1 Persons with morbid obesity a) have a body-mass index greater than or equal to 40 kg/m2. b) should be offered bariatric surgery as the initial treatment. c) have a relative risk of death similar to persons with a normal weight. d) who have had a Roux-en-Y gastric bypass are usually not able to maintain a body-mass index less than 35 kg/m2 over the long term. e) are frequently able to achieve a body-mass index less than 35 kg/m2 without operation over the long term without surgery. Critique: Morbid obesity is defined as a body-mass index greater than or equal to 40 kg/m2. According to a National Institutes of Health Consensus Statement, patients judged by experienced clinicians to have a low probability of success with nonsurgical measures, as demonstrated, for example, by failures in established weight control programs or reluctance by the patient to enter such a program, might be considered for surgery. The risk of death from all causes increases over the range of moderate and severe obesity for both men and women at any age. Late followup of isolated gastric bypass has demonstrated that a body-mass index below 35 kg/m2 can be achieved by 93% of patients with obesity or morbid obesity, and by 57% of patients with “super-obesity” (those with an initial body-mass index of 50 kg/m2 or greater). Although physician-supervised, very low calorie diets might have dramatic shortterm success, most patients regain their lost weight within 1 year. A minority of obese patients treated with diet therapy, pharmacologic therapy, dietary counseling, or behavioral therapy are able to maintain substantial longterm weight loss. Question 2 In a clinical decision analysis
J Am Coll Surg
a) only two treatment alternatives can be compared in any one decision analysis model. b) the results of a decision model are unaffected by the estimates of the model parameters. c) a utility is a quantitative measure of the relative desirability of an outcome or health state. d) a valid estimate of the optimal treatment strategy can be determined even if there are no known data on the probabilities of chance events and the value of the outcomes. e) treatment alternatives can be compared with respect to effectiveness or with respect to cost, but not both. Critique: Decision analysis can be used to select the optimal treatment choice from two or more treatment alternatives. The results of a decision analysis are heavily influenced by the values assigned to the probabilities of chance events, and to the utility values assigned to the outcomes. Sensitivity analysis is a method of systematically varying the values of the variables included in the model, to determine the effect of uncertainty in the estimation of these variables on the results. The conclusions of a model are valid only to the extent that the underlying decision tree is correct, and the estimates of the probabilities of chance events and treatment outcomes are realistic. A utility is a quantitative measure of the relative desirability of an outcome or health state. The outcome to be optimized in a decision analysis model can be a measure of effectiveness, such as expected survival or quality-adjusted survival, cost, or a costeffectiveness ratio. A cost-effectiveness analysis of intraoperative cholangiography in the prevention of bile duct injury during laparoscopic cholecystectomy Flum DR, Flowers C, Veenstra DL J Am Coll Surg 2003;196:385–393 Learning Objectives: To evaluate the cost implications of routine cholangiography in reducing the rate of common bile duct injury during cholecystectomy and to appreciate the components of and variability involved with formal cost analytic techniques. Question 1 Cost analysis a) uses base-case estimates that are the lowest values identified in the literature. b) compares the cost per quality-adjusted life years but does not allow for comparisons to other interventions. c) is an exact science.
Vol. 196, No. 3, March 2003
d) must include sensitivity analyses to be complete. e) divides the costs of the intervention into the costs of the outcome. Critique: Cost analysis is part of a set of analytic techniques that uses estimates from varied sources to determine the cost components of a given outcome. The best estimates of the probability of related events and costs of each event and outcome are obtained and used in comparative base-case models to determine the cost per event. By including the amount of life years saved and measurements of the quality of that remaining life in the outcomes, simple cost analysis becomes cost-effectiveness analysis. The benefit of including qualityadjusted life years as an outcome measure is that qualityadjusted life years are easily comparable across interventions. Health policy analysts can then compare various interventions to determine relative merits using a common comparator. Cost, cost-efffectiveness, and decision analysis are not exact sciences. Rather, these techniques are a more formalized means to evaluate medical decision-making using the best available data and assumptions based on those data. These techniques are considered to be better than judgments made in dayto-day clinical practice about the “worth” of certain interventions because they explicitly identify transition probabilities and allow for scrutiny of these underlying assumptions. There are usually no statistical tests to confirm a cost analysis, but a complete cost analysis includes a sensitivity analysis. Sensitivity analysis demonstrates the impact of variation in all the parameters being measured and so helps to evaluate the integrity of the analysis. In a properly developed model, variation in probabilities along the range of possible values should not impact the overall conclusions of the cost analysis. Question 2 Regarding the cost of cholangiograms in preventing CBD injury: a) This study assumes from observational studies that more widespread use of an intraoperative cholangiogram will decrease the rate of CBD injury. b) The cost of buying a fluroscope should not be considered when performing cost analysis. c) Only the durable costs of the cholangiogram catheter are relevant to determining costs.
Continuing Medical Education Program
503
d) The cost of malpractice litigation related to bile duct injury should be included in this type of cost analysis. e) Cholangiogram is only cost effective when applied to high-risk patients. Critique: The rate of bile duct injury is so low (1:200– 1:350) that a prospective study to evaluate whether cholangiograms reduce the rate of CBD injury would require more than 26,000 patients. Because it is unlikely that such a study will be performed, to understand the role of cholangiograms we must extrapolate from large population-based studies that show nearly a doubling in the rate of CBD injury when no cholangiogram is performed. This extrapolation is problematic because retrospective, observational studies cannot be used to ascribe cause and effect. Because there might be important confounders (both measured and unmeasured) in observational studies, they should only be used to describe associations. When multiple observational studies point out the same effect and the same magnitude of effect and when that link is biologically plausible, the strength of evidence supporting causality grows. But by epidemiologic standards this still falls short of a cause-and-effect relationship and requires that an assumption be made. Regarding the specifics of this cost analysis, a complete analysis includes the material costs of the cholangiogram catheter, the capital costs of purchasing a fluoroscope, and the opportunity costs of occupied operating room personnel and space. Including all these components in a cost analysis indicates that cholangiogram is cost-effective when applied by all surgeons and on all patients. Legal costs associated with the outcome are not typically included in formal cost analysis because it is assumed that these costs are already incorporated into the cost averaging of health care. This study demonstrates that cholangiogram use was cost-effective for all patients and surgeons. The costeffectiveness of cholangiogram is greater when it is applied by high-risk surgeons (early experience with cholecystectomy) or among higher-risk patients (those with pancreatitis and other acute biliary disease). Unfortunately, predicting who will have a bile duct injury during cholecystectomy is problematic, and routine cholangiogram use might be the only reasonable approach from a public health perspective.