Using treatment-tradeoff preferences to select diagnostic strategies: linking the ROC curve to threshold analysis.

Selection of optimal diagnostic strategies depends on the accuracy of diagnostic tests, the prevalence of disease, and the relative benefits and harms resulting from test/treatment choices. One can characterize diagnostic strategies according to their net benefit-to-harm ratios. Within the framework of expected-utility theory, the benefit-to-harm ratio is equivalent to the marginal tradeoff between erroneous and correct treatment choices. Consequently, a physician can identify his or her preferred strategy by asking the question: "How many additional treatment errors am I willing to make in order to treat one additional person correctly?" Family physicians were asked to indicate their lowest and highest acceptable tradeoff ratios in a survey about streptococcal pharyngitis. All 53 respondents indicated uncertainty about their preferred treatment-tradeoff ratios. For 58% of respondents, the midpoints of the acceptable range of tradeoff ratios corresponded to generally accepted diagnostic strategies: 1) test all or 2) treat if classic, test all others. In contrast, previously published patient utilities yield a treatment-tradeoff ratio that corresponds to the strategy of treating all cases. The analysis illustrates the linkage between the optimal operating point on a receiver operating characteristic (ROC) curve and the selection of a preferred diagnostic strategy based on treatment thresholds derived from benefit-to-harm ratios. The survey results indicate that physicians can respond directly to questions assessing their preferences for such treatment thresholds. Differences between patients and physicians have significant impacts on choices of test and treatment strategies.

Cost rounds: presentations by residents on the cost of care.

Cost rounds are conferences on ambulatory medical care presented by third-year residents at the University of Washington in Seattle. The content includes data from a chart audit, charges for services in the clinic and laboratory, and suggested management guidelines. The chart audits stimulate interest in the conferences, and they are feasible when residents are provided with ways to identify patients by diagnosis, specific medication, or laboratory test. This program is a sustainable method of involving residents in discussions about the quality and cost of the care they deliver.

A system for drug utilization review in ambulatory care.

BACKGROUND: It is more difficult to conduct drug utilization reviews in ambulatory care settings than in inpatient care settings. This is true for several reasons: it is harder to identify outpatients who are receiving specific medications; often there is less evidence on which to base clinical standards for drug use; and it is more difficult to ensure patient compliance with drug therapy. METHODS: This article describes a drug utilization review system designed to operate in ambulatory care clinics. The system consists of (1) a computerized database for efficient identification of patients who receive prescriptions for a specific medication, (2) clinic-wide consensus guidelines, (3) reminders in the medical record, (4) regular chart audits, and (5) feedback to physicians. RESULTS: Experience in monitoring the use of serum theophylline assays illustrates how this system can be used in an ambulatory care clinic. According to guidelines adopted in our clinic, overuse of assays is not a problem. The system of physician reminders and chart audits can help prevent underuse. CONCLUSIONS: Despite the difficulties in conducting drug utilization reviews in the ambulatory setting, a system based on clinic-wide guidelines is feasible and should be an integral part of quality assurance programs.

Divergent regulation of beta 2-adrenoceptors and adenylate cyclase in the Cyc- mouse T lymphoma cell line TL2-9.

The radiation leukemia virus-induced murine Cyc- T lymphoma cell line TL2-9 expressed one homogeneous population of beta 2-adrenoceptors based on competition curves of [125I]cyanopindolol with the specific antagonist ICI 118.551 and three beta-adrenergic agonists. These receptors were uncoupled from adenylate cyclase due to the absence of Gs. The catalytical unit was directly stimulated by MnCl2, forskolin, and even more markedly in the simultaneous presence of both reagents. In contrast, the enzyme was inhibited in the presence of Gpp[NH]p, probably through interaction with Gi. Indeed, this inhibitory effect was constrained by preincubating cells in the presence of pertussis toxin and a 41 kDa protein was specifically ADP-ribosylated in the presence of the toxin. This cell line was therefore analogous to the Cyc- cell line derived from the murine S49 lymphoma cell line. When added to the culture medium, butyrate (2 mM) induced beta 2-adrenoceptors, the expression of these uncoupled receptors depending on protein synthesis, as judged by inhibitory effects of cycloheximide. In contrast, dBcAMP (1 mM) and TPA (tumor-promoting agent phorbol ester) increased the rate of disappearance of beta 2-adrenoceptors. Butyrate, dBcAMP and TPA systematically decreased adenylate cyclase activity. Besides, TPA (but neither butyrate nor dBcAMP) reduced the efficacy of Gpp[NH]p in inhibiting adenylate cyclase, suggesting a proportionately higher alteration of Gi. We conclude that beta 2-adrenoceptors, uncoupled from adenylate cyclase, are regulated independently from the catalytical unit and Gi, in this Cyc- T lymphoma cell line.

The comprehensiveness of computer-assisted searches of the medical literature.

Bibliographic searches using MEDLINE, the National Library of Medicine computerized database, can usually be done in less time and with greater specificity than searches using Index Medicus. To use a computer-assisted bibliographic retrieval system to full advantage, it is necessary to understand the indexing system. The study reported here compares both the number and the relevance of references retrieved using various search terms for two clinical questions. Based on the outcomes of these searches, recommendations are made for clinicians who plan to use MEDLINE services.

Use of a clinical decision rule to diagnose streptococcal pharyngitis in hospital employees.

Some people with pharyngitis have clinical findings that are suggestive of either streptococcal or nonstreptococcal disease. In this study the published results of the accuracy of a clinical decision rule are used to calculate the probable outcomes of withholding antibiotics from some hospital employees or giving others treatment presumptively without testing for group A streptococcal disease. Cost-benefit analysis shows explicitly how selective testing results in a trade-off among costs, the number of people given treatment unnecessarily, and the number with untreated disease that may spread within the hospital. The best strategy depends on judgment, taking into account the nature of the employee's patient contact, the needs of the hospital, and the resources for infection control.

Selective testing for streptococcal pharyngitis in adults.

Some physicians test for group A streptococcal pharyngitis in all patients who have a sore throat, while others use a variety of clinical strategies to select patients to be tested. Using published data on the accuracy of a clinical decision rule, this benefit-cost analysis compares the calculated outcomes of 21 different management strategies applied to 1,000 hypothetical adults with pharyngitis. Strategies that best accomplish one physician's treatment goals may perform poorly when evaluated in a different practice setting or using different goals. The best strategies are identified for different treatment objectives and for different assumptions about the benefits of treatment so each physician can choose a strategy consistent with his or her preferences.

Using decision analysis to communicate the importance of quality assurance studies.

Decision analysis, which structures the information used by physicians in making medical decisions, has the potential for being a valuable quality assurance (QA) tool. Probability trees derived from decision analysis studies can be used to make quantitative, graphic connections between QA data and adverse medical outcomes. This article provides four hypothetical examples of how decision analysis studies can help providers understand the relationship between QA data and patient welfare.

Evaluating rapid tests for streptococcal pharyngitis: the apparent accuracy of a diagnostic test when there are errors in the standard of comparison.

The evaluation of new rapid antigen detection tests for streptococcal pharyngitis is complicated by the presence of errors in the standard of comparison. Even "gold standard" throat cultures are not perfectly accurate. This article is an analysis of how errors in the comparison cultures affect the apparent accuracy of new tests for streptococcal pharyngitis. One of the questions addressed is whether throat cultures performed in a physician's office are accurate enough to use as a standard in a clinical trial of a new rapid test. While the accuracy of office cultures is accepted by many to be adequate for diagnostic purposes, this analysis shows that when evaluating a new test stricter conditions must be placed on the accuracy of the cultures used for comparison.

Role of rapid tests for streptococcal pharyngitis in hospital infection control.

Rapid streptococcal antigen detection tests are now an alternative to throat cultures for diagnosing group A streptococcal pharyngitis. Used alone, they are not suitable for hospital infection control applications because of the risk that individuals with streptococcal pharyngitis and a falsely negative test will spread the infection within the institution. However, a rapid test may be an economical method for screening employees with pharyngitis, provided that a throat culture is performed for everyone with a negative test. Compared with the use of throat cultures alone, this strategy reduces the number of missed diagnoses and the number of work days lost. Cost-benefit analysis shows that over a wide range of streptococcal prevalence and carrier rate the total cost is also less with the use of rapid tests first. If the prevalence of streptococcal pharyngitis is very low, the use of cultures alone is more cost-effective.

Comparison of tests for streptococcal pharyngitis.

Rapid streptococcal antigen detection tests are now an alternative to throat cultures for diagnosing group A streptococcal pharyngitis. By applying existing knowledge to 1,000 theoretical patients, this study compares the diagnostic accuracy, costs, and benefits of "gold standard" throat cultures, less specific office cultures, and rapid streptococcal tests. With the new rapid tests, appropriate treatment for streptococcal pharyngitis can be started promptly without waiting for a culture result. Benefit-cost analysis of existing data shows that rapid tests have the potential to be more efficient than throat cultures in minimizing medical costs and time lost because of illness. These conclusions remained true over widely ranging assumptions about streptococcal prevalence, carrier rate, rheumatic fever attack rate, test cost, and test accuracy.