Predictors of common bile duct stones prior to cholecystectomy: a meta-analysis

BACKGROUND

The decision of whether or not to investigate for common bile duct stones before cholecystectomy utilizes clinical, laboratory, and radiologic information (indicators). There is tremendous individual variation among clinicians in the criteria used for making this decision. Our aim was to perform a meta-analysis of published data to estimate the performance characteristics of the most commonly used preoperative indicators of common bile duct stones.

METHODS

Using predetermined exclusion criteria, we selected articles from a MEDLINE search and bibliographic review. Weighted averages were used to determine summary sensitivity, specificity, and positive and negative likelihood ratios for each indicator for stones.

RESULTS

From 2221 citations identified, 22 studies met inclusion criteria. The 10 indicators examined were reported in a common fashion in three or more articles, and could be assessed preoperatively. Seven exhibited a specificity greater than 90%. Indicators with positive likelihood ratios of 10 or above were cholangitis, preoperative jaundice, and ultrasound evidence of common bile duct stones. Positive likelihood ratios for dilated common bile duct on ultrasound, hyperbilirubinemia, and jaundice ranged from almost 4 to almost 7. Elevated levels of alkaline phosphatase, pancreatitis, cholecystitis, and hyperamylasemia exhibited positive likelihood ratios of less than 3.

CONCLUSIONS

This meta-analysis has identified indicators for duct stones and ranked them according to likelihood ratios. These findings can be applied as guidelines for whether to investigate for duct stones before cholecystectomy.

The appropriateness of coronary artery bypass graft surgery in academic medical centers. Working Group of the Appropriateness Project of the Academic Medical Center Consortium

OBJECTIVE

To compare the appropriateness of use of coronary artery bypass graft (CABG) surgery in Academic Medical Center Consortium hospitals as judged 1) according to criteria developed by an expert panel, 2) according to revisions of those criteria made by cardiac surgeons from the Academic Medical Center Consortium, and 3) by review of cases by the surgeons responsible for those cases.

DESIGN

Retrospective, randomized medical record review.

SETTING

12 Academic Medical Center Consortium hospitals.

PATIENTS

Random sample of 1156 patients who had had isolated CABG surgery in 1990.

MAIN OUTCOME MEASURES

1) Percentage of patients with indications for which CABG surgery was classified as appropriate, Inappropriate, or of uncertain appropriateness and 2) percentage of cases in which CABG surgery was judged inappropriate or uncertain for which ratings changed after local case review.

RESULTS

Data were retrieved from medical records by trained abstractors using an explicit data collection instrument. Cases in which CABG surgery was judged to be inappropriate or uncertain were individually reviewed by the responsible surgeons. According to the expert panel ratings, 83% of the CABG operations (95% CI, 81% to 85%) were necessary, 9% (CI, 8% to 10%) were appropriate, 7% (CI, 5% to 8%) were uncertain, and 1.6% (CI, 0.6% to 2.5%) were inappropriate. These rates are almost identical to those found in a previous study that was done in New York State and that used the same criteria (in that study, 91% of operations were classified as necessary or appropriate, 7% were classified as uncertain, and 2.4% were classified as inappropriate). Rates of inappropriate procedures varied from 0% to 5% among the 12 member hospitals (P = 0.02). The Academic Medical Center Consortium cardiac surgeons revised 568 (24%) of the indications used by the expert panel. However, because those revisions altered the appropriateness ratings in both directions and affected only 50 cases (4%), the net effect of the revisions was slight: The rate of inappropriate CABG surgery increased from 1.6% to 1.9%. Local review found that data collection errors had caused erroneous ratings in 12.5% of 64 cases in which surgery had been classified as inappropriate or uncertain.

CONCLUSIONS

The Academic Medical Center Consortium hospitals had low rates of inappropriate and uncertain use of CABG surgery, regardless of the criteria used for assessment. Even though surgeons from the Consortium revised the appropriateness ratings extensively, their revisions had a negligible effect on the overall assessment of appropriateness. However, because of potential data collection errors, appropriateness criteria should be used for individual case audits only if supplemented by subsequent physician review.

Variations in the management of acute myocardial infarction. Importance of clinical measures of disease severity

OBJECTIVE

To determine the extent to which resource use for patients hospitalized with acute myocardial infarction varies with clinical status, and to see if an observed difference in resource use between two states can be explained by clinically detailed risk adjustment.

DESIGN

Retrospective review of the clinical characteristics and resource use of 342 patients hospitalised in two states with acute myocardial infarction.

DATA SOURCES

Merged data from three sources: a large, existing research database used in developing the Medicare Mortality Predictor Score, clinical data abstracted from medical charts specifically for this study, and Medicare Parts A and B claims records.

PATIENTS

A probability sample of Medicare patients hospitalized in 1986 with a diagnosis of acute myocardial infarction and residing in either Wisconsin or Washington state; patients dying within 30 days are oversampled.

MEASUREMENTS AND MAIN RESULTS

Although patients were clinically similar in the two states, there were systematic differences in resource use. Patients in Wisconsin spent more than one extra day in the intensive care unit (ICU) (2.8 vs 1.7) as well as more than one extra non-ICU day in the hospital (8.0 vs 6.5) than patients in Washington. Patients in Wisconsin were also more likely to receive an echocardiogram (35.6% vs 15.8%), nuclear ventriculogram (12.8% vs 4.1%), exercise tolerance test (21.5% vs 3.4), and Holter monitoring (5.4% vs 0%). (All p < .01.) Differences in utilization were greater for patients at lower risk of dying. The average cost of care was 20.8% higher in Wisconsin (p = .01); risk adjustment for clinical and other factors reduced this difference to 11.8%, but did not eliminate it (p = .04).

CONCLUSIONS

Patients with acute myocardial infarction vary in resource use as a function of clinical factors present at admission and occurring during the hospital stay; comparisons that do not take account of these factors may not discriminate well between providers who care for sicker patients and those who are inefficient. The greater use of resources for patients in Wisconsin is at least partially explained by differences in clinical characteristics that are not presently captured in administrative data.

Cholesterol lowering and the use of healthcare resources. Results of the Scandinavian Simvastatin Survival Study

BACKGROUND

Advances in the treatment of cardiovascular disease have increased costs; annual cardiovascular healthcare expenditure in the United States currently exceeds $100 billion. Physicians and third-party payers need to assess the economic impact of treatments that reduce cardiovascular morbidity and mortality.

METHODS AND RESULTS

The Scandinavian Simvastatin Survival Study is a randomized, double-blind, placebo-controlled trial in which simvastatin reduced the risk of death by 30% (P=.0003) over the median follow-up period of 5.4 years in patients with previous myocardial infarction or stable angina pectoris as a result of a 42% reduction in the risk of coronary deaths (P=.00001). In the present report, data prospectively collected from hospital admissions were analyzed to evaluate the impact of simvastatin on healthcare resource use and perform a cost-minimization analysis. In the placebo group (n=2223), there were 1905 hospitalizations (average duration, 7.9 days) for acute cardiovascular events or coronary revascularization procedures among 937 patients, whereas in the simvastatin group (n=2221), there were 1403 such hospitalizations (average duration, 7.1 days) among 720 patients (all differences, P<.0001). The corresponding number of hospital days was 15089 and 9951 in the two groups, respectively (34% reduction,P<.0001). In the United States, the resulting reduction in hospitalization costs over the 5.4 years of the trial would be $3872 per patient, reducing the effective cost of simvastatin by 88% to $0.28 per day.

CONCLUSIONS

In addition to reducing mortality and morbidity in coronary heart disease patients, simvastatin markedly reduces use of hospital services, thus offsetting most of its cost.

Polymerase chain reaction for the diagnosis of HIV infection in adults. A meta-analysis with recommendations for clinical practice and study design

PURPOSE

To do a meta-analysis of studies that have evaluated the sensitivity and specificity of polymerase chain reaction (PCR) assay for the diagnosis of human immunodeficiency virus (HIV) infection in adults. Evaluating the performance of PCR is difficult because in certain clinical situations, the sensitivity or specificity of PCR may exceed those of the current reference standard tests (enzyme immunoassay followed by confirmatory Western blot analysis). Therefore, an additional goal was to develop recommendations for 1) the design of future evaluative studies of PCR and 2) the use of PCR in persons with suspected HIV infection.

DATA SOURCES

Studies published between 1988 and 1994 that were identified in a search of 17 computer databases, including MEDLINE, and abstracts identified from conference proceedings.

STUDY SELECTION

Studies were included if DNA amplification by PCR was done on peripheral blood mononuclear cells from adults. Ninety-six studies met the inclusion criteria.

DATA EXTRACTION

Data were extracted independently by two reviewers. Study design was assessed independently by two investigators blinded to study results.

RESULTS

Reported sensitivities for PCR range from 10% to 100%, and specificities range from 40% to 100%. A summary receiver-operating characteristic curve based on all 96 studies has a maximum joint sensitivity and specificity (upper left point on the curve, where sensitivity equals specificity) of 97.0% to 98.1%. If the threshold value that defines a positive PCR result is chosen so that sensitivity is higher than 98.1%, specificity will decrease to less than 98.1%. Conversely, if the threshold value that defines a positive PCR result is chosen so that specificity is greater than 98.1%, sensitivity will decrease to less than 98.1%. If sensitivity and specificity are chosen to be equal, the corresponding false-positive rate is 1.9% to 3.0%. At the maximum joint sensitivity and specificity, the positive predictive value of PCR ranges from 34% to 85% as the prevalence of HIV increases from 1.0% to 10%. We identified seven areas in which study design could be modified to 1) reduce susceptibility to bias in estimates of the sensitivity and specificity of PCR and 2) to increase the generalizability of the study results. These modifications will also help to overcome methodologic problems created by the lack of a reference standard test.

CONCLUSIONS

The PCR assay is not sufficiently accurate to be used for the diagnosis of HIV infection without confirmation. Use of PCR for the diagnosis of HIV in adults should be limited to situations in which antibody tests are known to be insufficient. Future studies of PCR performance should be sufficiently large and should use adequate reference standard tests and standardized methods for the performance of PCR. Specimens should be evaluated by persons blinded to clinical status and to the results of other diagnostic tests for HIV infection.

Doxycycline compared with azithromycin for treating women with genital Chlamydia trachomatis infections: an incremental cost-effectiveness analysis

OBJECTIVE

To compare the economic consequences of doxycycline therapy with those of azithromycin therapy for women with uncomplicated cervical chlamydial infections.

DESIGN

Decision analysis in which the health outcomes, costs, and cost-effectiveness of two provider-administered treatment strategies for women with uncomplicated cervical chlamydial infections were compared: 1) initial therapy with doxycycline, 100 mg orally twice daily for 7 days (estimated cost, $5.51) and 2) initial therapy with azithromycin, 1 g orally administered as a single dose (estimated cost, $18.75).

RESULTS

Under baseline assumptions, the azithromycin strategy incurred fewer major and minor complications and was less expensive overall than the doxycycline strategy despite a higher initial cost for acquiring antibiotic agents. In univariate sensitivity analyses, the azithromycin strategy prevented more major complications but was more expensive than the doxycycline strategy when doxycycline effectiveness was greater than 0.93. In a multivariate sensitivity analysis combining 11 parameter estimates selected so that the cost-effectiveness of the doxycycline strategy would be maximized relative to that of the azithromycin strategy, the azithromycin strategy resulted in fewer complications but was more costly. The incremental cost-effectiveness was $521 per additional major complication prevented. However, if the difference in the cost of azithromycin and doxycycline decreased to $9.80, the azithromycin strategy was less expensive and more effective, even under these extreme conditions.

CONCLUSIONS

On the basis of the best available data as derived from the literature and experts, the azithromycin strategy was more cost-effective than the doxycycline strategy for women with uncomplicated cervical chlamydial infections. Despite the dominance of the azithromycin strategy over the doxycycline strategy, the adoption of the azithromycin strategy may be limited by the practical financial constraints of our currently fragmented health care system, in which the costs and benefits of preventing chlamydia sequelae are often incurred by different components of the system.

The cost-effectiveness of terazosin and placebo in the treatment of moderate to severe benign prostatic hyperplasia

OBJECTIVES

To evaluate the cost-effectiveness and functional status effects of terazosin, an alpha(1)-adrenoceptor antagonist, compared with placebo in the treatment of men with moderate to severe, symptomatic, benign prostatic hyperplasia (BPH).

METHODS

Prospective, randomized, double-blind, placebo-controlled multicenter trial of 2084 patients was conducted at 15 academic regional centers and 141 community-based satellite centers. Information about the use of health care resources and non-disease-specific functional status measures was collected by a standardized telephone interview of patients at baseline and every month thereafter for 12 months. Other information, such as American Urologic Association (AUA) disease-specific functional status scores, was obtained from the patient study records. Patients had a mean age of 65.7 years (range, 46 to 94), with a clinical diagnosis of BPH. At baseline men had at least moderate BPH symptoms by AUA Symptom score (13 or more) and Bother Score (8 or more). On entry, patients at regional sites had peak urinary flow rates 15 mL/s or less and total voided urine volumes 150 mL or greater. A total of 1053 patients were randomized to terazosin and 1031 to placebo treatment. Primary outcome measures included payments for all direct medical resource consumption (inpatient care, emergency department care, outpatient care, and medications); changes in three AUA disease-specific functional status indicators, (Symptom, Bother, and Quality of Life scores), and non-disease-specific functional status measures (days of work loss, days of customary activity loss, and days of bed rest).

RESULTS

Total payments for health care resource (including study drug medication), adjusted to reflect 1000 patients per treatment group, were $3,781,803 and $3,568,263 in the placebo and terazosin groups, respectively. All three AUA disease-specific functional status scores improved significantly more in the terazosin group than in the placebo group. We found no difference between terazosin and placebo in all three nonspecific functional status measures.

CONCLUSIONS

Compared with placebo, terazosin therapy for moderate to severe symptomatic BPH results in approximately equivalent payments for direct medical care, better disease-specific functional status improvement, and comparable change in non-disease-specific functional status measures.

Clinical economics and noncoronary vascular disease

With the evolution of the U.S. health care system toward managed care, there is increasing concern with the economics of health care delivery. Several important basic principles and approaches are reviewed here. First, costs, not charges, must be assessed, and these costs must include both direct medical costs, in the form of resources consumed, and indirect costs, such as productivity losses. Second, the simplest type of analysis, cost-identification analysis, is rarely appropriate to the clinical situation in which interventions with potentially different risks and benefits are being compared. Cost-benefit analysis may be more useful, but accurate assessment of benefits in monetary units is often not possible. Cost-effectiveness analysis expresses costs in monetary units, but quantitates benefits in natural units of outcome, such as survival or altered function. Results are expressed, for example as cost per year of life saved. In the more common clinical situation, however, outcomes include preferences, and the utility of interventions is quantitated in cost per quality adjusted life-year. All of these types of assessment are limited, to some extent, by differences in patient populations and in patient preferences. Probably the greatest contribution from clinical economic analysis occurs in the relatively common situation in which two alternative interventions both have advantages and disadvantages-that is, neither of the choices is both more effective and less expensive. Incremental cost-effectiveness of different interventions can be used instead, and this, empirically, has been shown to have great clinical relevance.

Omeprazole or ranitidine plus metoclopramide for patients with severe erosive oesophagitis. A cost-effectiveness analysis

The objective of this study was to evaluate the clinical and economic effects of 2 clinical strategies for treating severe (grade II and above) erosive oesophagitis or poorly responsive gastro-oesophageal reflux disease. A single-blind, randomised controlled trial of up to 8 weeks' duration was undertaken comparing omeprazole with ranitidine plus metoclopramide in patients with severe and symptomatic erosive oesophagitis (endoscopic grade II and above). Two cost-effectiveness ratios were calculated: cost per healed patient and cost per symptom-free day. The study perspective was that of the payer or insurer of medical care. Healing rates were significantly higher among omeprazole-treated patients than among those who received ranitidine/metoclopramide at 4 weeks (68.5% vs 30.4%; p < 0.01) and overall (81.5% vs 45.7%; p < 0.01). Overall, mean gastrointestinal-related direct medical costs per healed patient were lower for the omeprazole group ($US189.60) than for the ranitidine/metoclopramide group ($US319.28). The incremental cost of an additional cure with omeprazole compared with ranitidine/metoclopramide was $US24.05. The overall average cost per symptom-free day was lower in the omeprazole group ($US7.88) than in the ranitidine/metoclopramide group ($US10.81). The incremental cost to obtain an additional symptom-free day with omeprazole, compared with ranitidine/metoclopramide, was $US1.41. In conclusion, superior efficacy at comparable cost is achieved by omeprazole compared with ranitidine/metoclopramide in the treatment of patients with severe erosive oesophagitis.

Hospital adoption of medical technology: an empirical test of alternative models

OBJECTIVE

This study examines hospital motivations to acquire new medical technology, an issue of considerable policy relevance: in this case, whether, when, and why hospitals acquire a new capital-intensive medical technology, magnetic resonance imaging equipment (MRI).

STUDY DESIGN

We review three common explanations for medical technology adoption: profit maximization, technological preeminence, and clinical excellence, and incorporate them into a composite model, controlling for regulatory differences, market structures, and organizational characteristics. All four models are then tested using Cox regressions.

DATA SOURCES

The study is based on an initial sample of 637 hospitals in the continental United States that owned or leased an MRI unit as of 31 December 1988, plus nonadopters. Due to missing data the final sample consisted of 507 hospitals. The data, drawn from two telephone surveys, are supplemented by the AHA Survey, census data, and industry and academic sources.

PRINCIPAL FINDING

Statistically, the three individual models account for roughly comparable amounts of variance in past adoption behavior. On the basis of explanatory power and parsimony, however, the technology model is "best." Although the composite model is statistically better than any of the individual models, it does not add much more explanatory power adjusting for the number of variables added.

CONCLUSIONS

The composite model identified the importance a hospital attached to being a technological leader, its clinical requirements, and the change in revenues it associated with the adoption of MRI as the major determinants of adoption behavior. We conclude that a hospital's adoption behavior is strongly linked to its strategic orientation.

Evaluation of the complication rate as a measure of quality of care in coronary artery bypass graft surgery

OBJECTIVE

To determine whether hospital rankings based on complication rates provide the same information as hospital rankings based on mortality rates.

DESIGN

A retrospective study of in-hospital death, complication, and death following complication (failure to rescue). Hospitals were ranked using residuals based on the difference between the observed and the expected number of events (from logistic regression models); rankings were compared using Spearman rank correlations.

SETTING

Hospitals performing coronary artery bypass graft (CABG) surgery in the 1991 and 1992 MedisGroups National Comparative Data Bases. PATIENTS AND DATA SETS: Record abstraction data for 16,673 patients who underwent CABG procedures at 57 hospitals, linked with data from the 1991 American Hospital Association Annual Survey.

RESULTS

After adjusting for patient admission severity of illness, there were low correlations between hospital rankings based on death or failure to rescue and those rankings based on complication (death vs complication, r = 0.07, P = .58; failure to rescue vs complication, r = -0.22, P = .11). In addition, many hospital characteristics that are generally associated with a higher quality of care were associated with higher complication rates but with expected or lower-than-expected mortality rates.

CONCLUSIONS

Hospital rankings based on complication rates provide different information than those based on mortality rates. Until more is known about these differences, complication rates should not be used to judge hospital quality of care in CABG surgery.

Sex differences in patient acceptance of cardiac transplant candidacy

BACKGROUND

The overwhelming majority of cardiac transplant recipients are men. This can be partially explained by the earlier age at which heart failure develops in men. However, an underrepresentation of women also may reflect physician referral or selection biases or differences in patients' access to or acceptance of heart transplantation.

METHODS AND RESULTS

We investigated whether sex bias occurred in the transplant candidate selection process at a single cardiac transplant center. We prospectively evaluated 386 individuals < 70 years of age (295 men, 91 women) referred for management of moderate to severe heart failure and/or cardiac transplant evaluation. Age, race, sex, heart failure type, New York Heart Association class, left ventricular ejection fraction, peak exercise oxygen consumption, disease duration, resting hemodynamic measurements, comorbidity index score, health insurance coverage, and estimated household income were recorded. For patients not accepted for transplantation, the reason for rejection was also obtained. Univariable and multivariable (logistic regression) analyses were performed comparing men and women and patients accepted and those not accepted for cardiac transplantation. Female sex was independently associated with rejection for cardiac transplantation (odds ratio, 2.57; P = .01). However, the reason for rejection (odds ratio, 2.57; P = .01). However, the reason for rejection was more likely to be patient self-refusal for women than for men (29% versus 9%), and female sex was independently associated with patient self-refusal (odds ratio, 4.68; P = .003). When patients who refused transplant were reclassified as accepted for transplant, female sex was no longer associated with nonacceptance. However, lower patient income was associated with nonacceptance for transplant.

CONCLUSIONS

We found no evidence of sex bias in the selection of cardiac transplant recipients at our center. These findings suggest that the underrepresentation of women among cardiac transplant recipients may result, in part, from a sex difference in treatment preference, with a decreased willingness of women to undergo transplantation. The reasons for the difference in acceptance rates between men and women need to be elucidated.

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.

A methodology for the economic assessment of picture archiving and communication systems

Most economic studies of picture archiving and communication systems (PACS) to date, including our own, have focused on the perspectives of the radiology department and its direct costs. However, many researchers have suggested additional cost savings that may accrue to the medical center as a whole through increased operational capacity, fewer lost images, rapid simultaneous access to images, and other decreases in resource utilization. We describe here an economic analysis framework we have developed to estimate these potential additional savings. Our framework is comprised of two parallel measurement methods. The first method estimates the cost of care actually delivered through online capture of charge entries from the hospital's billing computer and from the clinical practices' billing database. Multiple regression analyses will be used to model cost of care, length of stay, and other estimates of resource utilization. The second method is the observational measurement of actual resource utilization, such as technologist time, frequency and duration of film searches, and equipment utilization rates. The costs associated with changes in resource use will be estimated using wage rates and other standard economic methods. Our working hypothesis is that after controlling for the underlying clinical and demographic differences among patients, patients imaged using a PACS will have shorter lengths of stay, shorter exam performance times, and decreased costs of care. We expect the results of our analysis to explain and resolve some of the conflicting views of the cost-effectiveness of PACS.

Penetrating neck trauma: sensitivity of clinical examination and cost-effectiveness of angiography

PURPOSE

To evaluate penetrating neck trauma for (a) sensitivity of the clinical examination as an indicator of clinically significant vascular injury, and (b) cost-effectiveness of performing screening diagnostic angiography.

METHODS

The medical records of all patients with penetrating neck trauma presenting at our institution over 4 years were retrospectively reviewed. Injuries were classified into one of three anatomic zones and classified into four mutually exclusive groups based on the extent of vascular injury; (a) no vascular injury; (b) minor vascular abnormality; (c) major vascular abnormality without a change in clinical management; or (d) any injury requiring a change in clinical management. Cost data were also obtained for each patient's hospitalization.

RESULTS

There were 111 patients with penetrating neck trauma. No statistically significant difference between the sensitivities of the clinical examination or angiography for the detection of vascular injury were detected. Of the 48 patients who had vascular injuries, 45 had an abnormal clinical findings (93.7% sensitivity). None of the remaining 3 patients with vascular injury and normal clinical findings would have had their treatment altered by the results of angiography. The calculated cost of using angiography as a screening tool for vascular injury in patients with normal clinical findings was approximately $3.08 million per central nervous system event prevented.

CONCLUSION

Our study suggests that in patients with zone II penetrating neck injuries the clinical examination is sufficient to detect significant vascular lesions and that screening angiography may not be indicated. Because our sample size was relatively small and the mean follow-up only 13.3 days, further investigation is needed to demonstrate definitively the lack of usefulness of screening angiography.

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.