Association of dialyzer reuse with hospitalization and survival rates among U.S. hemodialysis patients: do comorbidities matter?

The objective of this study was to determine whether the associations between reuse of hemodialyzers and higher rates of death and hospitalization persist after adjustment for comorbidity. This was a nonconcurrent cohort study of survival and hospitalization rates among 1491 U.S. chronic hemodialysis patients beginning treatment in 1986 and 1987. The impact of dialyzer reuse was compared across three survival models: an unadjusted model, a "base" model adjusted only for demographics and renal diagnosis, and an "augmented" model additionally adjusted for comorbidities. We found that reuse of dialyzers was associated with a similarly higher rate of death in analyses unadjusted for confounders (relative risk [RR] 1.25, 95% confidence interval [CI] 0.97-1.61), adjusted for demographics and renal diagnosis (RR 1.16, 95% CI 0.96-1.41), and analyses additionally adjusted for comorbidities (RR = 1.25, CI, 1.03, 1.52). Reusing dialyzers was also associated with a greater rate of hospitalization that was stable regardless of adjustment procedures. We conclude that higher rates of death and hospitalization associated with dialyzer reuse persist regardless of adjustment for demographic characteristics or baseline comorbidities. These findings amplify concerns that there exists elevated morbidity among hemodialysis patients treated in facilities that reuse hemodialyzers. Although the association we observed was not confounded by comorbidity, a cause-and-effect relationship between dialyzer reuse and morbidity could not be proved because of the inability to control for aspects of care other than dialyzer reuse.

The effect of race and sex on physicians' recommendations for cardiac catheterization

BACKGROUND

Epidemiologic studies have reported differences in the use of cardiovascular procedures according to the race and sex of the patient. Whether the differences stem from differences in the recommendations of physicians remains uncertain.

METHODS

We developed a computerized survey instrument to assess physicians' recommendations for managing chest pain. Actors portrayed patients with particular characteristics in scripted interviews about their symptoms. A total of 720 physicians at two national meetings of organizations of primary care physicians participated in the survey. Each physician viewed a recorded interview and was given other data about a hypothetical patient. He or she then made recommendations about that patient's care. We used multivariate logistic-regression analysis to assess the effects of the race and sex of the patients on treatment recommendations, while controlling for the physicians' assessment of the probability of coronary artery disease as well as for the age of the patient, the level of coronary risk, the type of chest pain, and the results of an exercise stress test.

RESULTS

The physicians' mean (+/-SD) estimates of the probability of coronary artery disease were lower for women (probability, 64.1+/-19.3 percent, vs. 69.2+/-18.2 percent for men; P<0.001), younger patients (63.8+/-19.5 percent for patients who were 55 years old, vs. 69.5+/-17.9 percent for patients who were 70 years old; P<0.001), and patients with nonanginal pain (58.3+/-19.0 percent, vs. 64.4+/-18.3 percent for patients with possible angina and 77.1+/-14.0 percent for those with definite angina; P=0.001). Logistic-regression analysis indicated that women (odds ratio, 0.60; 95 percent confidence interval, 0.4 to 0.9; P=0.02) and blacks (odds ratio, 0.60; 95 percent confidence interval, 0.4 to 0.9; P=0.02) were less likely to be referred for cardiac catheterization than men and whites, respectively. Analysis of race-sex interactions showed that black women were significantly less likely to be referred for catheterization than white men (odds ratio, 0.4; 95 percent confidence interval, 0.2 to 0.7; P=0.004).

CONCLUSIONS

Our findings suggest that the race and sex of a patient independently influence how physicians manage chest pain.

Health maintenance organization penetration and the practice location choices of new physicians: a study of large metropolitan areas in the United States

OBJECTIVES

The rapid growth of health maintenance organizations is reshaping the practice opportunities available to physicians. The practice location decisions of new physicians provide a sensitive bellwether of these changes. This study assessed the effect of health maintenance organization penetration on practice location for physicians completing graduate medical education (GME).

METHODS

Conditional logit regression analysis was used to determine the effect of health maintenance organization penetration on practice location, controlling for other market characteristics. Subjects were physicians who finished GME between 1989 and 1994 and who located in one of the 98 US metropolitan areas with more than 500,000 population. The outcome measure was the particular metropolitan area chosen by each new physician.

RESULTS

Early in the study period, new generalists were significantly more likely to locate in metropolitan areas with high health maintenance organization penetration than in low penetration areas, whereas new specialists' practice location choices were not associated with health maintenance organization penetration. The likelihood of choosing a high penetration relative to a low penetration area declined with time, however, for both generalists and specialists. Consequently, by the end of the study period, health maintenance organization penetration had a weak but significant negative effect on practice location for generalists and a strong negative influence on practice location for specialists.

CONCLUSIONS

New generalists who completed graduate medical education between 1989 and 1994 were more likely than new specialists to locate in market areas with high health maintenance organization penetration; however, the proportions of both generalists and specialists who chose high penetration areas decreased during the study period. This finding may reflect reduced practice opportunities in high penetration areas relative to low penetration areas as health maintenance organizations' systems for controlling utilization began to yield results. Alternatively, new physicians may have become more hesitant to accept available positions in high penetration areas.

Physician opportunity costs in physician practice cost functions

Estimation of cost functions for physician firms is problematic because many physicians are self-employed, and the marginal opportunity cost of physician labor is not observed. In this paper, we show how to recover marginal costs and conventional measures of economies of scale from cost functions that condition on the amount of physician labor input. In addition, we introduce the new concepts of marginal nonphysician input costs and 'behavioral' economies of scale, which reflect the structure of costs when physician labor input moves along a utility-maximizing expansion path. Our results could be useful in the design of resource-based physician fee schedules.

Indications for and outcomes of cholecystectomy: a comparison of the pre and postlaparoscopic eras

PURPOSE

Examine changing patient characteristics and surgical outcomes for patients undergoing cholecystectomy at five community hospitals in 1989 and 1993.

PROCEDURES

In a retrospective chart review, data were gathered regarding gallstone disease severity, type of admission, patient age, number of comorbidities, American Society of Anesthesiologists (ASA) Physical Status Classification, length of stay, and multiple outcomes of surgery.

MAIN FINDINGS

The volume of nonincidental cholecystectomies increased 26%, from 1611 in 1989 to 2031 in 1993. Nearly all of the increase occurred among patients with uncomplicated cholelithiasis and with elective admissions. In 1993, lengths of stay were significantly shorter and percentages of complications were significantly lower for infectious, cardiac, pulmonary, and gastrointestinal complications when controlling for patient case-mix characteristics. There were more major intraoperative complications (unintended wounds or injuries to the common bile duct, bowel, blood vessel(s), or other organs) in 1993.

CONCLUSIONS

Different types of patients underwent cholecystectomy in 1993 compared with patients in 1989, which supports the hypothesis of changing thresholds. Statements supporting the safety of cholecystectomy in the laparoscopic era were borne out when controlling for differences in patient characteristics.

Diagnostic coding and medical rehabilitation length of stay: their relationship

OBJECTIVE

To determine if diagnostic information provided in the form of International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes improves rehabilitation length of stay (LOS) prediction when used in combination with the Functional Independence Measure-Function Related Groups (FIM-FRGs) classification system.

DESIGN

Various models characterizing diagnostic information using ICD-9-CM codes were created that included individual ICD-9-CM codes and groupings of those codes by organ or etiology involved. Each method was evaluated using linear regression with the natural logarithm of LOS as the dependent variable. Separate validation data sets were held back to quantify the incremental effect of diagnosis when combined with the FIM-FRG classification system.

SETTING

Records from 252 rehabilitation facilities and hospital units across the nation.

PATIENTS

Analyses were undertaken using 82,646 records from patients discharged in 1992.

RESULTS

The addition of ICD-9-CM diagnostic information to the FIM-FRG classification system increased the variance explained by a maximum of 1.9%, from 31.5% to 33.4%.

CONCLUSIONS

Refinement of the FIM-FRGs to include ICD-9-CM diagnoses does not appear warranted on the basis of the small increase in the percentage of explained variance in LOS. We believe the lack of improved prediction with the addition of ICD-9-CM codes relates primarily to incomplete coding practices and to the effect of patients' diagnoses being absorbed in variables as already expressed by the FIM-FRG system. Although ICD-9-CM codes, overall, did not greatly improve LOS prediction, they appeared to have some impact in certain impairment categories.

Segmentation of hospital markets: where do HMO enrollees get care?

Commercially insured and Medicare patients who are not in health maintenance organizations (HMOs) tend to use different hospitals than HMO patients use. This phenomenon, called market segmentation, raises important questions about how hospitals that treat many HMO patients differ from those that treat few HMO patients, especially with regard to quality of care. This study of patients undergoing coronary artery bypass graft surgery found no evidence that HMOs in southeast Florida systematically channel their patients to high-volume or low-mortality hospitals. These findings are consistent with other evidence that in many areas of the country, incentives for managed care plans to reduce costs may outweigh incentives to improve quality.

Development of function-related groups version 2.0: a classification system for medical rehabilitation

OBJECTIVE

To present a new version (2.0) of the Functional Independence Measure-Function Related Group (FIM-FRG) case-mix measure.

DATA SOURCE/STUDY SETTING

85,447 patient discharges from 252 freestanding facilities and hospital units contained in the 1992 Uniform Data System for Medical Rehabilitation.

STUDY DESIGN

Patient impairment category, functional status at admission to rehabilitation, and patient age were used to develop groups that were homogeneous with respect to length of stay. Within each impairment category patients were randomly assigned to one data set to create the system (through recursive partitioning) or a second set for validation. Clinical and statistical criteria were used to increase the percentage of patients classified, expand the impairment categories of FIM-FRGs Version 1.1, and evaluate the incremental predictive ability of coexisting medical diagnoses. Predictive stability over time was evaluated using 1990 discharges.

PRINCIPAL FINDINGS

In Version 2.0, the percentage of patients classified was increased to 92 percent. Version 2.0 includes two new impairment categories and separate groups for patients admitted to rehabilitation for evaluation only. Coexisting medical diagnoses did not improve LOS prediction. The system explains 31.7 percent of the variance in the logarithm of LOS in the 1992 validation sample, and 31.0 percent in 1990 discharges.

CONCLUSIONS

FIM-FRGs Version 2.0 includes more specific impairment categories, classifies a higher percentage of patient discharges, and appears sufficiently stable over time to form the basis of a payment system for inpatient medical rehabilitation.

Quality assessment in contracting for tertiary care services by HMOs: a case study of three markets

BACKGROUND

Few studies have examined the provision of tertiary care services by managed care organizations (MCOs). Moreover, little is known about the role of quality assessment and quality assurance mechanisms in the contracting process. Site visits were conducted in 1995 in three geographic areas to describe and evaluate the contracting processes for tertiary care services, especially neonatal intensive care and coronary artery bypass graft surgery, of health maintenance organizations (HMOs).

METHODS

Three market areas in the United States, each with differing levels of "maturity", as primarily defined in terms of managed care penetration, were selected for study. Interviews were conducted with HMO and hospital managers about the processes for identifying potential tertiary care hospitals and mechanisms for quality assessment and quality improvement (QI) that are considered in the contracting process.

FINDINGS

The most sophisticated contracting arrangements were found in the most mature market-where HMOs select hospitals for tertiary care services based on both the price and quality of services, with quality assessed through both objective and subjective data. Yet in all three markets, quality assessment was the least well-developed component of tertiary care contracting. Even in the mature market, we found inconsistent use of even validated quality or outcomes measures in hospital contracting.

CONCLUSION

The potential of MCOs to increase quality depends on their ability to identify high-quality hospitals and their willingness to direct enrollees to those hospitals. Yet inconsistent evidence was found that mechanisms for evaluating and rewarding quality are being fully adopted in the three markets studied.

Externalities in hospitals and physician adoption of a new surgical technology: an exploratory analysis

Much recent work on the economics of new technology adoption has investigated the roles of information and externalities. However, studies of technology adoption by physicians have not addressed these issues. This paper examines the adoption by general surgeons of laparoscopic cholecystectomy, a new surgical procedure which was introduced in 1989. The paper addresses the informational and cost externalities which may be generated when the first surgeon in a hospital adopts a new procedure. The findings suggest that access to information about laparoscopic cholecystectomy influenced surgeons' adoption behavior, and that externalities in hospitals may have hastened the diffusion of the procedure.

Effect of dialyzer reuse on survival of patients treated with hemodialysis

OBJECTIVE

To evaluate the impact of dialyzer reuse on the survival of US hemodialysis patients.

STUDY DESIGN AND PARTICIPANTS

Nonconcurrent cohort study of 27938 patients beginning hemodialysis in the United States in 1986 and 1987.

MAIN OUTCOME MEASURE

Patient survival.

RESULTS

Dialysis in freestanding facilities reprocessing dialyzers with the combination of peracetic and acetic acids was associated with greater mortality than treatment in facilities not reprocessing dialyzers (rate ratio [RR],1.10, 95% confidence interval [CI], 1.02-1.18; P=.02) In contrast, there was no significant difference between survival in freestanding facilities reprocessing dialyzers with either formaldehyde (RR,1.03, 95% CI, 0.96-1.10; P=.45) or glutaraldehyde (RR, 1.13, 95% CI, 0.95-1.35, P=.18) and survival in freestanding facilities not reprocessing dialyzers. Among freestanding facilities reprocessing dialyzers, use of peracetic/acetic acid was associated with a higher rate of death than use of formaldehyde (RR = 1.08, 95% CI, 1.01-1.14; P=.02). There was no statistical difference between survival in hospital-based facilities reprocessing dialyzers with either peracetic/acetic acid (RR=0.95, 95% CI, 0.85-1.06; P=.40), formaldehyde (RR=1.06, 95% CI, 0.98-1.15; P=.12), or glutaraldehyde (RR=1.09, 95% CI, 0.71-1.67; P=.70) and survival in hospital-based facilities not reprocessing dialyzers. In addition, choice of sterilant was not associated with a statistically significant difference in survival among hospital-based facilities reprocessing dialyzers.

CONCLUSIONS

Dialysis in freestanding facilities reprocessing dialyzers with peracetic/acetic acid may be associated with worse survival than dialysis in free-standing facilities not reprocessing dialyzers or in those reprocessing with formaldehyde. We were unable to determine whether these relationships arose from greater comorbidity among patients treated in facilities using peracetic/acetic acid, poor quality of dialysis procedures in these facilities, or direct toxicity of peracetic/acetic acid. These findings raise important concerns about potentially avoidable mortality among US hemodialysis patients treated in dialysis facilities reprocessing hemodialyzers.

Survival of Medicare patients after enrollment in hospice programs

BACKGROUND

Each year more than 220,000 Medicare beneficiaries receive care from hospice programs designed to enhance the quality of the end of life. Enrollment requires certification by a physician that the patient has a life expectancy of less than six months. We examined how long before death patients enrolled in hospice programs.

METHODS

Using 1990 Medicare claim data, we analyzed the characteristics and survival of 6451 hospice patients followed for a minimum of 27 months with respect to mortality.

RESULTS

The patients' mean age was 76.4 years; 92.4 percent were white. Half the patients were women, and 80.2 percent had cancer of some type. The most common diagnoses were lung cancer (21.4 percent), colorectal cancer (10.5 percent), and prostate cancer (7.4 percent). The median survival after enrollment was only 36 days, and 15.6 percent of the patients died within 7 days. At the other extreme, 14.9 percent of the patients lived longer than six months. Survival varied substantially according to diagnosis, even after adjustment for age and co-existing conditions. The unadjusted survival after enrollment was shortest for those with renal failure, those with leukemia or lymphoma, and those with liver or biliary cancer; it was longest for those with chronic lung disease, those with dementia, and those with breast cancer. Patients at for-profit, larger, outpatient, or newer hospices lived longer after enrollment than those in other types of hospice programs.

CONCLUSIONS

Most patients who enter hospice care do so late in the course of their terminal illnesses. The timing of enrollment in hospice programs varies substantially with the characteristics of the patients and the hospices.

Falling cholecystectomy thresholds since the introduction of laparoscopic cholecystectomy

OBJECTIVES

To determine whether cholecystectomy rates among the elderly increased following the introduction of laparoscopic cholecystectomy in 1989, and to assess whether changes in rates were accompanied by lower clinical thresholds for performing cholecystectomy.

DESIGN

Time-series quasi-experimental design based on quarterly observations from 1986 to 1993. Data were obtained from Medicare hospital discharge files for Pennsylvania.

PATIENTS

Medicare patients aged 65 years or older who resided in Pennsylvania, did not have end-stage renal disease, and underwent cholecystectomy in Pennsylvania from 1986 to 1993.

MAIN OUTCOME MEASURES

Cholecystectomy rates per 1000 elderly Medicare beneficiaries, stage of gallstone disease (uncomplicated vs complicated) at cholecystectomy, type of admission (elective vs urgent/emergent), patient age and comorbidities, and 30-day postoperative mortality.

RESULTS

Cholecystectomy rates increased 22% from 1989 to 1993. The proportions of cholecystectomy patients with uncomplicated gallstone disease and with elective admissions declined from 1986 to 1989 but then increased rapidly after laparoscopic cholecystectomy was introduced. In contrast, the age distribution and comorbidities of cholecystectomy patients did not change during the study period. Postoperative mortality rates were stable from 1986 to 1989 but decreased thereafter.

CONCLUSIONS

Growth in cholecystectomy rates following the introduction of laparoscopic cholecystectomy was accompanied by evidence of lower clinical thresholds for performing surgery. The normative, or prescriptive, implications of lower cholecystectomy thresholds require further analyses that consider lower direct medical costs and indirect costs and reduced postoperative morbidity after laparoscopic cholecystectomy.

Diffusion of laparoscopic cholecystectomy among general surgeons in the United States

Introduced in 1989, laparoscopic cholecystectomy has rapidly become the treatment of choice for symptomatic gallstones. This study describes the diffusion of laparoscopic cholecystectomy among general surgeons; assesses the importance of various reasons for surgeons adopting the procedure; and examine the influence of surgeon, practice, and health care market characteristics on the timing of adoption. The data were obtained from a survey of a national sample of surgeons. Most surgeons (81%) adopted laparoscopic cholecystectomy by early 1992. More than three fourths of adopters identified the desire to keep up with the state-of-the-art and improved patient outcomes as very or extremely important reasons for adoption. Results of proportional hazards regression analysis indicate that individual surgeons' adoption behavior generally was consistent with expected utility maximization in an uncertain new technological environment. Of particular interest, fee-for-service payment and more competitive practice settings and markets were associated with earlier adoption. These findings suggest that the "technological imperative" and surgeons' perception of the relative clinical and financial advantages of laparoscopic cholecystectomy were important reasons for the rapid diffusion of laparoscopic cholecystectomy. Policies that accelerate current trends toward payment of physicians based on salary or capitation and promote the growth of multispecialty group practice could slow the diffusion of new physician-based product innovations in health care.

Outcomes of open cholecystectomy in the elderly: a longitudinal analysis of 21,000 cases in the prelaparoscopic era

OBJECTIVE

We sought to obtain unbiased estimates of open cholecystectomy outcomes in a population-based cohort of elderly patients during the immediate prelaparoscopic era.

METHODS

Medicare claims data were used to identify 21,131 patients aged 65 years or more who underwent open cholecystectomy in Pennsylvania between 1986 and 1989 and to develop longitudinal histories of hospitalizations and physician services utilization for these patients. Study patients were divided into three groups: simple cholecystectomy, cholecystectomy with intraoperative cholangiography (IOC) alone, and cholecystectomy with common bile duct exploration (CBDE). Outcomes examined included 30- and 90-day postoperative mortality rates and postoperative complications.

RESULTS

Postoperative mortality rates in all patients was 2.1% at 30 days and 3.6% at 90 days. Patients in the CBDE group had a significantly higher mortality rate than those in the simple cholecystectomy or IOC groups; adjusted for differences in case mix, the mortality rate in the CBDE group was 47% higher at 30 days and 29% higher at 90 days. Rates of retained or recurrent common duct stones, bile duct stricture, and recurrent biliary tract surgery by 42 to 60 months after cholecystectomy were 2.8%, 0.4%, and 1.0%, respectively. CBDE was a strong risk factor for these complications. In contrast, the IOC group had a significantly lower risk of having clinically manifest retained or recurrent common duct stones develop by 42 months after operation.

CONCLUSIONS

This study provides an unbiased assessment of open cholecystectomy outcomes necessary for future comparisons of open and laparoscopic cholecystectomy in elderly patients. Estimates of the excess mortality rates associated with CBDE provide a benchmark for assessing the outcomes of alternative strategies for managing common duct stones during laparoscopic cholecystectomy. Findings regarding the rates of retained or recurrent common bile duct stones in patients undergoing simple cholecystectomy and IOC challenge widespread beliefs about the limited clinical importance of unsuspected common duct stones, at least in the elderly population, and are relevant to the debate about routine IOC.

Revised estimates of diagnostic test sensitivity and specificity in suspected biliary tract disease

BACKGROUND

The purpose of this study was to estimate the sensitivity and specificity of diagnostic tests for gallstones and acute cholecystitis.

METHODS

All English-language articles published from 1966 through 1992 about tests used in the diagnosis of biliary tract disease were identified through MEDLINE. From 1614 titles, 666 abstracts were examined and 322 articles were read to identify 61 articles with information about sensitivity and specificity. Application of exclusion criteria based on clinical and methodologic criteria left 30 articles for analysis. Cluster-sampling methods were adapted to obtain combined estimates of sensitivities and specificities. Adjustments were made to estimates that were biased because the gold standard was applied preferentially to patients with positive test results.

RESULTS

Ultrasound has the best unadjusted sensitivity (0.97; 95% confidence interval, 0.95 to 0.99) and specificity (0.95; 95% confidence interval, 0.88 to 1.00) for evaluating patients with suspected gallstones. Adjusted values are 0.84 (0.76 to 0.92) and 0.99 (0.97 to 1.00), respectively. Adjusted and unadjusted results for oral cholecystogram were lower. Radionuclide scanning has the best sensitivity (0.97; 95% confidence interval, 0.96 to 0.98) and specificity (0.90; 95% confidence interval, 0.86 to 0.95) for evaluating patients with suspected acute cholecystitis; test performance is unaffected by delayed imaging. Unadjusted sensitivity and specificity of ultrasound in evaluating patients with suspected acute cholecystitis are 0.94 (0.92 to 0.96) and 0.78 (0.61 to 0.96); adjusted values are 0.88 (0.74 to 1.00) and 0.80 (0.62 to 0.98).

CONCLUSIONS

Ultrasound is superior to oral cholecystogram for diagnosing cholelithiasis, and radionuclide scanning is the test of choice for acute cholecystitis. However, sensitivities and specificities are somewhat lower than commonly reported. We recommend estimates that are midway between the adjusted and unadjusted values.

Four methods for characterizing disability in the formation of function related groups

The Functional Independence Measure-Function Related Groups (FIM-FRGs) were developed to classify medical rehabilitation inpatients into homogeneous groups based on length of stay (LOS). Patients are first grouped into clinically relevant rehabilitation impairment categories, then by functional status, as expressed by the FIM, and in certain cases by patient age. The statistical approach used to form the final groupings was a recursive partitioning algorithm applied to the FIM scores and patient age within impairment category. This analysis compares four FIM-FRG classification schemes developed from four scale sets that combine FIM items differently: (1) use of the 18 FIM items as separate variables, (2) the combination of FIM items into six clinical subscales, (3) the combination of the six clinical subscales into motor and cognitive subscales, and (4) the combination of all FIM items into a single scale. The FIM-FRG schemes explain similar amounts of variance in the logarithm of LOS and contain approximately equal numbers of FRGs. The motor and cognitive subscale scheme is recommended for use in payment, however, this scheme and the other schemes have additional uses. Each FRG scheme provides different insight into the clinical relationship between disability and LOS.

Using Medicare claims for outcomes research

Medicare claims databases have several advantages for use in constructing episodes of care for outcomes research. They are population-based, relatively inexpensive to obtain, include large numbers of cases, and can be used for long-term follow-up. However, the sheer size of these claims databases, along with their primarily administrative (as opposed to clinical) nature, requires that researchers take special care in using them. The 10 PORTs using Medicare claims provided information on their approach to several key issues in working with these data, including: 1) identifying the index cases or patient cohorts to be studied; 2) defining the length of the episode; and 3) measuring outcomes. This paper reports the experience and knowledge gained by these PORTs in using these claims to create and analyze episodes of care.

A case-mix classification system for medical rehabilitation

Dissatisfaction with Medicare's current system of paying for rehabilitation care has led to proposals for a rehabilitation prospective payment system, but first a classification system for rehabilitation patients must be created. Data for 36,980 patients admitted to and discharged from 125 rehabilitation facilities between January 1, 1990, and April 19, 1991, were provided by the Uniform Data System for Medical Rehabilitation. Classification rules were formed using clinical judgment and a recursive partitioning algorithm. The Functional Independence Measure version of the Function Related Groups (FIM-FRGs) uses four predictor variables: diagnosis leading to disability, admission scores for motor and cognitive functional status subscales as measured by the Functional Independence Measure, and patient age. The system contains 53 FRGs and explains 31.3% of the variance in the natural logarithm length of stay for patients in a validation sample. The FIM-FRG classification system is conceptually simple and stable when tested on a validation sample. The classification system contains a manageable number of groups, and may represent a solution to the problem of classifying medical rehabilitation patients for payment, facility planning, and research on the outcomes, quality, and cost of rehabilitation.

Would eliminating differences in physician practice style reduce geographic variations in cataract surgery rates?

This study uses Medicare physician-claims data to examine patient and physician contributions to variations in cataract surgery rates across U.S. metropolitan areas. Utilization is modelled as having two phases: the decision to seek an ophthalmologist's care, which is made by patients, and the decision to perform surgery on patients who seek care, which is partially controlled by ophthalmologists. Under this model, the effect of physician practice style on cataract surgery rates occurs through the influence of practice style on the second phase of utilization. Variation in patient care-seeking behavior contributed to the variation in the rate of cataract surgery. Moreover, multivariate regression analyses found that cataract surgery rates were influenced by economic and sociodemographic variables in predictable ways. Using the regression results, a "purged" cataract surgery rate that was free of any possible influence of physician practice style was calculated. Variation in the purged surgery rate was only slightly lower than variation in the observed surgery rate, suggesting that eliminating practice style as a factor in physician decision making (e.g., through practice guidelines) would reduce variations in cataract surgery rates by only a small amount.

Effects of the relative fee structure on the use of surgical operations

OBJECTIVE

The goal is to develop a theoretical and empirical framework for investigating how the demand for an operation may be affected by the fee for the operation (the own-price) and by fees for other services provided by surgeons in the same specialty (the cross-price). The theory suggests an empirical test of whether surgeons create demand for surgery.

DATA SOURCES AND STUDY SETTING

The study examines the use of 11 frequently performed surgical operations by elderly Medicare enrollees in a cross-section of 316 U.S. metropolitan areas. Medicare physician claims and enrollment files for 1986 are the principal sources of data.

STUDY DESIGN

Using econometric methods, a structural demand equation modified to include the own-price and the cross-price is estimated for each study operation.

PRINCIPAL FINDINGS

The theory suggests that the utilization response to changes in fees may differ among operations depending on whether demand creation occurs and on the interplay of distinct own-price and cross-price effects. However, the results of the empirical analyses are inconclusive regarding the most appropriate economic model of surgical utilization. Both neoclassical behavior and demand creation are observed, but technical limitations of the analyses, including the cross-sectional design of the study, preclude definitive inferences.

CONCLUSIONS

Despite the lack of definitive empirical results, the study has several implications for future research regarding the effect of changes in fees on surgical utilization. In particular, future studies should consider the roles of distinct own-price and cross-price effects, examine the importance of the supply-demand balance in physician services markets, and assess whether typologies of operations that are based on the strictness of their clinical indications predict the appropriate economic model of utilization.

Racial differences in the elderly's use of medical procedures and diagnostic tests

OBJECTIVES

This study sought to examine racial differences in the use of medical procedures and diagnostic tests by elderly Americans.

METHODS

We used 1986 physician claims data for a 5% national sample of Medicare enrollees aged 65 years and older to study 32 procedures and tests. For each service, we calculated the age- and sex-adjusted rate of use by race and the corresponding White-Black relative risk.

RESULTS

Whites were more likely than Blacks to receive 23 services, and for many of these services, the differences in use were substantial. In contrast, Blacks were more likely than Whites to receive seven services. Whites had a particular advantage in access to higher-technology or newer services. Racial differences in use persisted among elders who had Medicaid in addition to Medicare coverage and increased among rural elders.

CONCLUSIONS

There are pervasive racial differences in the use of medical services by elderly Americans that cannot be explained by differences in the prevalence of specific clinical conditions. Financial barriers to care do not fully account for these findings. Race may exacerbate the impact of other barriers to access.

Effects of lower surgical fees on the use of physician services under Medicare

BACKGROUND AND OBJECTIVE

The changes in physician fees that will occur under the resource-based Medicare Fee Schedule (MFS) are similar to those that took place under the Omnibus Budget Reconciliation Act of 1987 (OBRA 87), when Medicare fees for selected "overpriced" procedures and diagnostic tests were reduced. To gain insight regarding the changes in utilization that may occur under the MFS, this study examines the effects of the OBRA 87 fee reductions on the use of physician services by Medicare patients.

DATA AND METHODS

The five specialties that were most affected by the OBRA 87 fee reductions were studied: ophthalmology, thoracic surgery, urology, orthopedic surgery, and gastroenterology. Medicare physician claims files for 1987 and 1989 were used to obtain data on utilization and fees. Multivariate regression analysis was used to assess the effect of changes in fees on changes in utilization.

RESULTS

The best estimate of the effect of the OBRA 87 fee reductions on overall physician-services utilization, obtained by pooling the five study specialties, was that every 1% decrease in fees led to a 0.09% decrease in the volume and complexity of services (95% confidence interval, 0.49% decrease to 0.31% increase). This result was not sensitive to minor changes in the covariates included in the regression model.

CONCLUSION

To calculate payment levels during the transition to the MFS, the Health Care Financing Administration assumed that physicians whose Medicare revenue declines under the MFS will increase service volume and complexity enough to make up one half of the lost revenue. The findings of this study suggest that the Health Care Financing Administration's assumption was, at best, extreme.

Medicare patients' use of overpriced procedures before and after the Omnibus Budget Reconciliation Act of 1987

OBJECTIVES

Under the Omnibus Budget Reconciliation Act of 1987, Medicare reduced physician fees for 12 procedures identified as overprices. This paper describes trends in the use of these procedures and other physician services by Medicare patients during the 4-year period surrounding the implementation of the 1987 budget act.

METHODS

Medicare physician claims files were used to develop trends in physician-services use from 1986 to 1989. Services were grouped into four categories: overpriced procedures, other surgery, medical care, and ancillary tests.

RESULTS

Growth in the volume of overpriced procedures slowed substantially after the 1987 budget act was implemented. Moreover, the reduction in the rate of volume growth for these procedures differed little among specialities or areas. In comparison, the rate of volume growth fell modestly for other surgery, was unchanged for medical care, and increased for ancillary tests.

CONCLUSIONS

Increases do not necessarily occur in the volume of surgical procedures whose Medicare fees are reduced. Although the conclusions that may be drawn from a descriptive analysis are limited, these findings suggest that concerns that the resource-based Medicare fee schedule will lead to higher surgery rates may be unwarranted.

Assessing physicians' estimates of the probability of coronary artery disease: the influence of patient characteristics

The authors assessed physicians' probability estimates of coronary artery disease (CAD) in 250 patients undergoing a screening exercise stress test. True likelihood of disease (prevalence) was derived from the literature. Discrimination and calibration were assessed by comparing physicians' probability estimates and prevalence using pairwise comparisons, rank correlation, and linear regression. There were differences in the discriminative abilities of the physicians based on patient characteristics. For example, the physicians had better discriminative ability for patients with typical cardiac chest pain compared with atypical chest pain. The physicians were able to predict the prevalence of CAD in broad groups of patients. However, they overestimated probabilities for patients with low prevalence of disease and underestimated probabilities for patients with high prevalence of disease. The authors conclude that physicians make consistent errors in the use of probability estimates. The quality of these estimates depends on patient characteristics such as type of chest pain and true likelihood of disease.

Impact of the Medicare fee schedule on an academic department of medicine

OBJECTIVE

To examine the effect of the Medicare Fee Schedule (MFS) on Medicare revenues in the department of medicine at an urban academic medical center after the MFS is fully implemented.

METHODS

Department revenues from Medicare were compared with projected revenues using the MFS proposed by the Health Care Financing Administration on June 5, 1991. National Medicare claims data were used to determine differences in service mix between community and academic internists and the impact of the geographic component of the MFS on department revenues.

RESULTS

Department revenues from Medicare in 1996 are projected to be 25.5% lower under the MFS than if the current system had continued. Subspecialty sections that perform large numbers of procedures and special tests had the largest decrease in revenues (eg, gastroenterology, -29.8%); however, this did not differ greatly from decreases in sections that mainly provide visits and consultations (eg, general internal medicine, -24.7%).

CONCLUSION

The proposed MFS is projected to lead to substantial reductions in department revenues from Medicare. While relative values for services and geographic location will play a role in how individual departments fare under the MFS, the value of the conversion factor used in the final MFS will be the factor of greatest importance.

Geographic variation in relative fees under Medicare

Little is known about geographic variation in Medicare's relative fee structure. Using 1986 Part B Medicare claims data, ratios among physician fees for surgical procedures belonging to small families of closely related procedures, excluding outliers, were found to vary up to twofold. Under Medicare's current system of physician payment, physicians in different areas face different financial incentives for performing one procedure in preference to possible alternatives. Changes in incentives under a resource-based Medicare fee schedule will be more pervasive than previously recognized.

Admission source to the medical intensive care unit predicts hospital death independent of APACHE II score

This study was conducted to determine if the source of admission to the medical intensive care unit (MICU) is associated with hospital death independent of the Acute Physiology and Chronic Health Evaluation (APACHE) II score. We calculated APACHE II scores and predicted risks of hospital death for 235 patients who were admitted to the MICU. The predicted death rate was the same as the actual rate for patients who were admitted directly from the emergency department (25% vs 22%), but was less than the actual rate for patients who were transferred from hospital floors (38% vs 55%), the medical intermediate care unit (32% vs 59%), and other hospitals (21% vs 36%). Logistic regression analysis confirmed an independent association between the MICU admission source and risk of death. Our findings suggest that APACHE II does not measure illness severity accurately in all patients who are admitted to intensive care units. If our results are generalizable, using APACHE II to compare intensive care outcomes among hospitals could lead to wrong conclusions about quality of care. Improving predictions of hospital death rates among patients who are in MICUs may require the inclusion of new types of information in the classification system.

Hyporeninemic hypoaldosteronism in a patient with cirrhosis and ascites

A patient with cirrhosis and coexistent hyporeninemic hypoaldosteronism secondary to diabetic nephropathy rapidly formed ascites despite marked reductions in plasma aldosterone concentration and urinary aldosterone excretion. To my knowledge, this association has not been previously reported. This case supports the concept that hyperaldosteronism is not a necessary component of the salt retention of advanced liver disease. Furthermore, it suggests that certain renal disorders should be considered in cases of cirrhosis and ascites with decreased plasma renin activity.