2015 年 36 巻 1 号 p. 13-24
Measuring the relative performance of a new treatment in the post-marketing environment is often challenging due to the lack of suitable control. We explore a case-only method to estimate the relative incidence of adverse events in disseminated intravascular coagulation (DIC) patients for comparison of two treatments. We proposed a heuristic approach that borrows its intuition from the self-controlled case series method with modification to the selection of control period. In DIC patients, the method of taking the post-treatment period for self-control is inappropriate because patients generally begin with a high risk of adverse events, which gradually improve with treatment. Instead, we randomly matched the timelines of DIC patients receiving competing treatments for baseline adjustment. Since only the timelines with at least an adverse event, that is, the “cases,” were required, the required sample sizes were smaller. Estimates were comparable to those obtained from the randomized trial and cohort method, and better than results based on the 1-to-1 matched case-control and binary response cohort design. Although the proposed approach loses the benefit of self-matching, with careful matching of patients and repeated random matching of time periods, the method has a potential to be useful for the post-market monitoring of new treatment for DIC or similar diseases.
