自我对照病例系列研究中相对发病率比的应用：综述
The use of relative incidence ratios in self-controlled case series studies: an overview.
作者信息
Hawken Steven, Potter Beth K, Little Julian, Benchimol Eric I, Mahmud Salah, Ducharme Robin, Wilson Kumanan
机构信息
Clinical Epidemiology Program, Ottawa Hospital Research Institute, 725 Parkdale Ave, Ottawa, ON, K1Y 4E9, Canada.
School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8 M5, Canada.
出版信息
BMC Med Res Methodol. 2016 Sep 23;16(1):126. doi: 10.1186/s12874-016-0225-0.
BACKGROUND
The self-controlled case series (SCCS) is a useful design for investigating associations between outcomes and transient exposures. The SCCS design controls for all fixed covariates, but effect modification can still occur. This can be evaluated by including interaction terms in the model which, when exponentiated, can be interpreted as a relative incidence ratio (RIR): the change in relative incidence (RI) for a unit change in an effect modifier.
METHODS
We conducted a scoping review to investigate the use of RIRs in published primary SCCS studies, and conducted a case-study in one of our own primary SCCS studies to illustrate the use of RIRs within an SCCS analysis to investigate subgroup effects in the context of comparing whole cell (wcp) and acellular (acp) pertussis vaccines. Using this case study, we also illustrated the potential utility of RIRs in addressing the healthy vaccinee effect (HVE) in vaccine safety surveillance studies.
RESULTS
Our scoping review identified 122 primary studies reporting an SCCS analysis. Of these, 24 described the use of interaction terms to test for effect modification. 21 of 24 studies reported stratum specific RIs, 22 of 24 reported the p-value for interaction, and less than half (10 of 24) reported the estimate of the interaction term/RIR, the stratum specific RIs and interaction p-values. Our case-study demonstrated that there was a nearly two-fold greater RI of ER visits and admissions following wcp vaccination relative to acp vaccination (RIR = 1.82, 95 % CI 1.64-2.01), where RI estimates in each subgroup were clearly impacted by a strong healthy vaccinee effect.
CONCLUSIONS
We demonstrated in our scoping review that calculating RIRs is not a widely utilized strategy. We showed that calculating RIRs across time periods is useful for the detection of relative changes in adverse event rates that might otherwise be missed due to the HVE. Many published studies of vaccine-associated adverse events could have missed/underestimated important safety signals masked by the HVE. With further development, our application of RIRs could be an important tool to address the HVE, particularly in the context of self-controlled study designs.
背景
自我对照病例系列（SCCS）是一种用于研究结局与短暂暴露之间关联的有用设计。SCCS设计可控制所有固定协变量，但仍可能发生效应修正。这可以通过在模型中纳入交互项来评估，当对交互项取指数时，可将其解释为相对发病率比（RIR）：效应修饰因子单位变化时相对发病率（RI）的变化。
方法
我们进行了一项范围综述，以调查已发表的原发性SCCS研究中RIR的使用情况，并在我们自己的一项原发性SCCS研究中进行了案例研究，以说明在SCCS分析中使用RIR来研究在比较全细胞（wcp）百日咳疫苗和无细胞（acp）百日咳疫苗背景下的亚组效应。通过这个案例研究，我们还说明了RIR在解决疫苗安全性监测研究中的健康疫苗接种者效应（HVE）方面的潜在效用。
结果
我们的范围综述确定了122项报告SCCS分析的原发性研究。其中，24项描述了使用交互项来检验效应修正。24项研究中有21项报告了特定分层的RI，24项中有22项报告了交互作用的p值，不到一半（24项中的10项）报告了交互项/RIR的估计值、特定分层的RI和交互作用p值。我们的案例研究表明，与acp疫苗接种相比，wcp疫苗接种后急诊就诊和住院的RI几乎高出两倍（RIR = 1.82，95% CI 1.64 - 2.01），其中每个亚组的RI估计值明显受到强烈的健康疫苗接种者效应的影响。
结论
我们在范围综述中表明，计算RIR不是一种广泛使用的策略。我们表明，跨时间段计算RIR有助于检测不良事件发生率的相对变化，否则这些变化可能会因HVE而被遗漏。许多已发表的疫苗相关不良事件研究可能遗漏/低估了被HVE掩盖的重要安全信号。随着进一步发展，我们对RIR的应用可能成为解决HVE的重要工具，特别是在自我对照研究设计的背景下。
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