Etzioni R D, Weiss N S
Program in Biostatistics, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA.
Am J Epidemiol. 1998 Aug 1;148(3):292-7. doi: 10.1093/oxfordjournals.aje.a009638.
In case-control studies of screening to prevent cancer mortality, exposure is ideally defined as screening that takes place within that period prior to diagnosis during which the cancer is potentially detectable using the screening modality under study. This interval has been called the detectable preclinical period (DPP). Misspecifying the duration of the DPP can bias the results of such studies. This article quantifies the impact of incorrectly estimating the duration of the DPP or using the correct average DPP but failing to consider its variability. The authors developed a computer simulation model of disease incidence and mortality with and without screening. The authors then selected cases and controls from the generated population and compared their screening histories. The results indicate that underestimation of the duration of the DPP generally leads to greater bias than does overestimation, but in both instances the extent of the bias is modified by the relative length of the DPP and the average interscreening interval. In practice, the authors recommend that to prevent a falsely low estimate of the effectiveness of a screening test in reducing mortality, a high percentile of the DPP distribution be used when analyzing the results of case-control studies of screening.
在旨在预防癌症死亡的筛查病例对照研究中，理想情况下，暴露被定义为在诊断前的那段时期内进行的筛查，在此期间，使用所研究的筛查方式有可能检测出癌症。这段间隔被称为可检测的临床前期（DPP）。错误指定DPP的持续时间可能会使此类研究的结果产生偏差。本文量化了错误估计DPP持续时间或使用正确的平均DPP但未考虑其变异性所产生的影响。作者开发了一个有筛查和无筛查情况下疾病发病率和死亡率的计算机模拟模型。然后作者从生成的人群中选择病例和对照，并比较他们的筛查历史。结果表明，低估DPP的持续时间通常比高估导致更大的偏差，但在这两种情况下，偏差程度都受到DPP的相对长度和平均筛查间隔的影响。在实践中，作者建议，为防止在分析筛查病例对照研究结果时错误地低估筛查试验在降低死亡率方面的有效性，在分析时应使用DPP分布的高百分位数。
