Understanding treatment-subgroup effect in primary and secondary prevention of cardiovascular disease: An exploration using meta-analyses of individual patient data

Background and Objective: Recommendations for preventing cardiovascular (CV) disease are currently separated into primary and secondary prevention. We hypothesize that relative effects of interventions for CV prevention are not different across primary and secondary prevention cohorts. Our aim was to test for differences in relative effects on CV events in common preventive CV interventions across primary and secondary prevention cohorts. Methods and Results: A systematic search was performed to identify individual patient data (IPD) meta-analyses that included both primary and secondary prevention populations. Eligibility assessment, data extraction, and risk of bias assessment were conducted independently and in duplicate. We extracted relative risks (RR) with 95% confidence intervals (95% CI) of the interventions over patient-important outcomes and estimated the ratio of RR for primary and secondary prevention populations. We identified five eligible IPDs representing 524,570 participants. Quality assessment resulted in overall low-to-moderate methodological quality. We found no subgroup effect across prevention categories in any of the outcomes assessed. Conclusion: In the absence of significant treatment-subgroup interactions between primary and secondary CV prevention cohorts for common preventive interventions, clinical practice guidelines could offer recommendations tailored to individual estimates of CV risk without regard to membership to primary and secondary prevention cohorts. This would require the development of reliable ASCVD risk estimators that apply across both cohorts.