To empirically evaluate the concordance of effect estimates between case-only and parallel group designs and to identify predictors of discrepancies.MEDLINE and EMBASE databases were searched through June 31, 2013. Studies that used both a case-only (case crossover or self-controlled case series) and a parallel group design (cohort or case-control) were identified. Spearman correlation coefficient was used to evaluate the concordance between designs. Z-scores were used to assess whether differences in the effect estimates were common, using an absolute threshold value of 1.96. A prediction model was built to identify predictors of discrepancies.The search identified 1,367 articles of which 53 were included for analysis. In total, 519 comparisons were made. The correlation coefficient between case-only vs. parallel group studies was 0.64 (P < .001). In 221 of the 519 comparisons (43

作者：Koen Bernardus, Pouwels；Bianca, Mulder；Eelko, Hak

来源：Journal of clinical epidemiology 2016 年 71卷