Khoury M J, Newill C A, Chase G A
Am J Public Health. 1985 Oct;75(10):1204-8. doi: 10.2105/ajph.75.10.1204.
To assess the usefulness of screening for risk factors, we derived arithmetic relationships between screening parameters (sensitivity, specificity, and positive predictive value PPV) and risk factor frequency, disease frequency and relative risk. We evaluated these relationships in the special case of genetic markers and disease susceptibility. It can be shown that even in the face of very large relative risks, sensitivity and positive predictive value are affected by the relative magnitude of disease and genetic marker frequencies. When the genetic marker is less frequent than the disease, PPV increases with increasing relative risk but sensitivity remains low. When the genetic marker is more frequent than the disease, sensitivity increases with increasing relative risk but PPV remains low. When marker and disease frequencies are equal, both PPV and sensitivity increase with increasing relative risks, but very high relative risks (greater than 100) have to be obtained for rare diseases. Depending on the goals of the screening program, these relationships can be used to predict the relative magnitudes of false positives (low PPV) and false negatives (low sensitivity). This approach can be generalized to evaluate nongenetic risk factors in screening programs as well.
为评估危险因素筛查的效用，我们推导了筛查参数（敏感性、特异性和阳性预测值PPV）与危险因素频率、疾病频率及相对风险之间的算术关系。我们在基因标记物与疾病易感性的特殊情况下评估了这些关系。结果表明，即使面对非常高的相对风险，敏感性和阳性预测值仍受疾病和基因标记物频率相对大小的影响。当基因标记物的频率低于疾病频率时，阳性预测值随相对风险的增加而升高，但敏感性仍然较低。当基因标记物的频率高于疾病频率时，敏感性随相对风险的增加而升高，但阳性预测值仍然较低。当标记物和疾病频率相等时，阳性预测值和敏感性均随相对风险的增加而升高，但对于罕见疾病而言，必须获得非常高的相对风险（大于100）。根据筛查项目的目标，这些关系可用于预测假阳性（低阳性预测值）和假阴性（低敏感性）的相对大小。这种方法也可推广用于评估筛查项目中的非遗传危险因素。
