University of Wisconsin-Madison, Middleton, WI 53562, USA.
Cancer Epidemiol Biomarkers Prev. 2012 Jun;21(6):881-6. doi: 10.1158/1055-9965.EPI-11-1066. Epub 2012 Apr 6.
Increasing numbers of individuals are choosing to opt out of population-based sampling frames due to privacy concerns. This is especially a problem in the selection of controls for case-control studies, as the cases often arise from relatively complete population-based registries, whereas control selection requires a sampling frame. If opt out is also related to risk factors, bias can arise.
We linked breast cancer cases who reported having a valid driver's license from the 2004-2008 Wisconsin women's health study (N = 2,988) with a master list of licensed drivers from the Wisconsin Department of Transportation (WDOT). This master list excludes Wisconsin drivers that requested their information not be sold by the state. Multivariate-adjusted selection probability ratios (SPR) were calculated to estimate potential bias when using this driver's license sampling frame to select controls.
A total of 962 cases (32%) had opted out of the WDOT sampling frame. Cases age <40 (SPR = 0.90), income either unreported (SPR = 0.89) or greater than $50,000 (SPR = 0.94), lower parity (SPR = 0.96 per one-child decrease), and hormone use (SPR = 0.93) were significantly less likely to be covered by the WDOT sampling frame (α = 0.05 level).
Our results indicate the potential for selection bias due to differential opt out between various demographic and behavioral subgroups of controls. As selection bias may differ by exposure and study base, the assessment of potential bias needs to be ongoing.
SPRs can be used to predict the direction of bias when cases and controls stem from different sampling frames in population-based case-control studies.
由于隐私问题，越来越多的人选择退出基于人群的抽样框架。这在病例对照研究中选择对照尤其成问题，因为病例通常来自相对完整的基于人群的登记处，而对照选择需要抽样框架。如果退出也与危险因素有关，则可能会出现偏差。
我们将报告拥有有效驾照的乳腺癌病例（来自 2004-2008 年威斯康星州妇女健康研究）与威斯康星州交通部（WDOT）的驾照主列表联系起来。此主列表排除了要求州不销售其信息的威斯康星州驾驶员。计算了多变量调整后的选择概率比（SPR），以估计使用此驾照抽样框架选择对照时潜在的偏差。
共有 962 例病例（32％）选择退出 WDOT 抽样框架。年龄<40 岁的病例（SPR = 0.90），收入未报告（SPR = 0.89）或超过 50,000 美元（SPR = 0.94），低胎次（SPR =每减少一个孩子 0.96）和激素使用（SPR = 0.93）的可能性明显较低，而 WDOT 抽样框架则涵盖了这些病例（α= 0.05 水平）。
我们的结果表明，由于控制组中各种人口统计学和行为亚组之间的退出存在差异，因此存在选择偏差的可能性。由于选择偏差可能因暴露和研究基础而异，因此需要持续评估潜在的偏差。
SPR 可用于预测在基于人群的病例对照研究中，病例和对照来自不同抽样框架时的偏倚方向。
