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一位临床医生在查阅有关疾病诊断的双向性试验方法(试验结果也可能为阳性,也可能为阴性)时,想要知道该试验是否对病人的诊断有帮助,那么,他首先需要了解当试验结果阴性时,病人患病的概率,称之为阳性试验结果预测值(PVpos)。他还需要了解试验结果阳性时,病人不患该病的概率(PVneg)和该试验方法的效率。所谓效率就是所有真阳性或真阴性的比例。遗憾的是PVpos、PVneg和效率,随着就诊人群患病率(先验概率)变化而变化。但试验方法的灵敏度和特异度不变。
A clinician who wants to know whether the test is helpful in the diagnosis of a patient when he has consulted a bidirectional test for diagnosis of the disease (the test result may also be positive or negative), he first needs to understand when the test When the result is negative, the probability of the patient’s illness is called the positive predictive result (PVpos). He also needs to understand the probability of the patient not suffering from the disease when the test results are positive (PVneg) and the efficiency of the test method. The so-called efficiency is the ratio of all true positive or true negative. Unfortunately, PVpos, PVneg, and efficiency vary with the prevalence of the patient (prior probability). However, the sensitivity and specificity of the test method remain unchanged.