Gayed N M, Kern D E
Division of General Internal Medicine, Johns Hopkins University School of Medicine, Francis Scott Key Medical Center, Baltimore, Maryland.
J Gen Intern Med. 1990 Jul-Aug;5(4):292-7. doi: 10.1007/BF02600393.
Knowledge of the prevalence (or pretest probability) of a disease is necessary for the interpretation of the results of a diagnostic test in a specific population of patients. This paper evaluates a formula for estimating the prevalence of a disease in a population, based on the proportion of patients with abnormal test results in that population and the known sensitivity and specificity of the test. The authors tested the formula by using it to estimate the prevalence of myocardial infarction in 215 patients with chest pain admitted to a coronary care unit, based on results of initial total creatine kinase determinations. The estimated prevalence was 30%. The true prevalence of myocardial infarction, based on established diagnostic criteria, was 25% (95% confidence interval 19.2%-30.8%). To further evaluate the formula, a sensitivity analysis was performed. Errors in estimated prevalence were inversely related to test sensitivity and specificity, positively related to the magnitude of the differences between presumed and true test sensitivity and specificity, and complexly related to the true prevalence of disease. This formula permits the estimation of prevalence of a disease in a population without resorting to the use of a "gold standard" test, which is often invasive or impractical. Situations are presented where the formula could be used to evaluate and improve the utilization of laboratory tests.
了解某种疾病的患病率（或验前概率）对于解释特定患者群体中诊断试验的结果是必要的。本文评估了一种基于某人群中检查结果异常的患者比例以及该检查已知的灵敏度和特异度来估算该人群中疾病患病率的公式。作者通过运用该公式，根据最初总肌酸激酶测定结果，对215名入住冠心病监护病房的胸痛患者的心肌梗死患病率进行了估算。估算的患病率为30%。基于既定诊断标准，心肌梗死的实际患病率为25%（95%置信区间为19.2%-30.8%）。为进一步评估该公式，进行了敏感性分析。估算患病率的误差与检查的灵敏度和特异度呈负相关，与假定的和实际的检查灵敏度及特异度之间差异的大小呈正相关，并且与疾病的实际患病率存在复杂的关系。该公式无需借助通常具有侵入性或不切实际的“金标准”检查，就能估算人群中疾病的患病率。文中列举了一些情形，在这些情形下该公式可用于评估和改善实验室检查的应用。
