OBJECTIVE:To describe strategies for using multiple clinical examination items to estimate disease probabilities; and to evaluate the diagnostic accuracy of each strategy.
DESIGN: Prospective observational study.SETTING: Medical preoperative evaluation clinic at a university-affiliated Veterans Affairs Medical Center.
PATIENTS:Previously reported consecutive series of patients referred for outpatient medical preoperative risk assessment.
MEASUREMENTS AND MAIN RESULTS:Pulmonary clinical examination and spirometry were the measurements. A strategy of using likelihood ratios (LRs) from seven clinical examination items was least accurate ( p Ͻ .0001). Three alternative strategies were equivalent in diagnostic accuracy ( p Ն .2): (1) using the single best clinical examination item and its LR, (2) using the LRs from three clinical examination items chosen by logistic regression, and (3) using the adjusted LRs chosen in strategy 2. When compared with using LRs from all seven items, the strategies of using three LRs chosen by logistic regression or using adjusted likelihood ratios better discriminated patients with airflow limitation from those without ( he clinical examination comprises the medical history and the physical examination. Each component of the clinical examination can be considered a separate diagnostic test. As such, clinicians must choose how to incorporate the numerous results obtained from eliciting the patient's history and performing a physical examination into their clinical decision making. Some of these results will be highly relevant, whereas others ought to have little impact on clinical decisions. This process of determining the relevance of clinical examination results is twofold: first, is the result statistically associated with the target disorder; and second, how much does the result contribute to the diagnosis above other clinical examination results? To make these decisions about relevance, clinicians need a summary measure of the impact of a given clinical examination result on the likelihood of the target disorder.Likelihood ratios (LRs) are convenient summary measures of diagnostic test performance. They describe the prevalence of a diagnostic test result in patients with a condition of interest versus the prevalence of the same test result among people without the condition. 1 Whether the test yields dichotomous, ordinal, or continuous results, LRs convey a similar type of diagnostic information. Clinicians can use LRs to modify their estimated prior odds of a target disorder to arrive at the posterior odds of the disorder. When there is a single diagnostic test, posterior odds is simply the product of prior odds and the LR for the test result.