Kafadar K, Prorok P C
Biometry Branch, National Cancer Institute, Bethesda, Maryland 20892-9044.
Stat Med. 1994;13(5-7):569-86. doi: 10.1002/sim.4780130519.
Screening tests are used frequently for control of diseases such as cancer. The increased survival time of screen-detected cases over those that are detected clinically may be due in part to 'lead time', or the length of time by which the disease is diagnosed earlier by screening in the presence or absence of any real extension in survival time. A realistic evaluation of screening needs to assess the true benefit of screening; that is, the length of time by which survival has been extended, beyond merely the time of the advanced diagnosis. The comparison of survival measured from time of entry between cases in a screening arm and in a control arm in randomized studies avoids the lead time bias. If the effects of average lead time and average benefit on survival are additive, these effects can be estimated by recognizing that (a) the difference in survival curves since time of diagnosis confounds benefit and lead time, but (b) the difference in survival curves since time of start of study involves benefit only. The method is evaluated on simulated data for its accuracy and may be used on data from randomized studies.
筛查测试经常用于癌症等疾病的控制。筛查发现的病例比临床诊断的病例生存时间延长，这可能部分归因于“领先时间”，即无论生存时间是否真正延长，通过筛查提前诊断疾病的时间长度。对筛查进行现实的评估需要评估筛查的真正益处；也就是说，生存时间延长的时长，而不仅仅是提前诊断的时间。在随机研究中，比较筛查组和对照组病例从入组时间开始测量的生存情况可避免领先时间偏差。如果平均领先时间和平均益处对生存的影响是相加的，那么通过认识到以下两点就可以估计这些影响：(a) 自诊断时间以来生存曲线的差异混淆了益处和领先时间，但 (b) 自研究开始时间以来生存曲线的差异仅涉及益处。该方法在模拟数据上评估了其准确性，可用于随机研究的数据。
