Bias reduction with an adjustment for participants' intent to dropout of a randomized controlled clinical trial
Bias reduction with an adjustment for participants' intent to dropout of a randomized controlled clinical trial
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DOI：
10.1177/1740774507083871
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发表时间：
2007-01-01
期刊：
影响因子：
2.7
通讯作者：
Hedeker, Donald
中科院分区：
文献类型：
--
作者：
Leon, Andrew C.;Demirtas, Hakan;Hedeker, Donald
损耗在随机对照临床试验中几乎无处不在，它带来了偏倚增加和统计效力降低的问题。虽然基于似然的统计模型（如混合效应模型）可以容纳不完整的数据，但有效推断通常需要假设可忽略的损耗。为了使可忽略性假设更合理，我们考虑了一个容易获得的协变量的值，该协变量已被其他人推荐，要求参与者对他们参加下一次评估会议的意图进行评级。方法在此，我们提出了一项模拟研究，比较了混合效应结果分析的偏倚和覆盖率，这些结果分析包括和不包括参加意愿作为协变量。对于我们研究的仿真规范，结果在减少偏差和提高精度方面是有希望的。具体来说，如果随时间变化的参加意向变量与减员、结果和治疗组相关，则通过将其纳入结果分析，可以大大减少偏倚。以这种方式调整的分析只会产生无偏的有效性估计，如果基于自评意图的损耗是可以忽略的。结论：在本研究的条件下，考虑参与者参加下一个评估会议的意图将减少损耗偏倚。该项目增加的负担很小，既可用于数据分析，也可用于确定有减员风险的参与者。
Background Attrition, which is virtually ubiquitous in randomized controlled clinical trials, introduces problems of increased bias and reduced statistical power. Although likelihood-based statistical models such as mixed-effects models can accommodate incomplete data, the assumption of ignorable attrition is usually required for valid inferences.Purpose In an effort to make the ignorability assumption more plausible, we consider the value of one readily obtained covariate that has been recommended by others, asking participants to rate their Intent to Attend the next assessment session.Methods Here we present a simulation study that compares the bias and coverage in mixed-effects outcome analyses that do and do not include Intent to Attend as a covariate.Results For the simulation specifications that we examined, the results are promising in the sense of reduced bias and greater precision. Specifically, if the time-varying Intent to Attend variable is associated with attrition, outcome and treatment group, bias is substantially reduced by including it in the outcome analyses.Limitations Analyses that are adjusted in this way will only yield unbiased estimates of efficacy if attrition is ignorable based on the self-rated intentions.Conclusions Accounting for participants' Intent to Attend the next assessment session will reduce attrition bias under conditions examined here. The item adds little burden and can be used both for data analyses and to identify participants at risk of attrition.