Cardio/Kidney Composite End Points: A Post Hoc Analysis of the EMPA-REG OUTCOME Trial

BACKGROUND: Cardio/kidney composite end points are clinically relevant but rarely analyzed in cardiovascular trials. This post hoc analysis of the EMPA-REG OUTCOME (Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients) trial evaluated cardio/kidney composite end points by 2 statistical approaches. METHODS AND RESULTS: A total of 7020 patients with type 2 diabetes mellitus and established cardiovascular disease were treated with empagliflozin 10 or 25 mg (n=4687) or placebo (n=2333) on top of standard care. Cardio/kidney composite end points studied were: (1) cardiac or kidney death, kidney failure, hospitalization for heart failure, sustained decline in estimated glomerular filtration rate >= 40% from baseline, or sustained progression to macroalbuminuria; (2) cardiac or kidney death, kidney failure, hospitalization for heart failure, or sustained estimated glomerular filtration rate decline >= 40% from baseline; and (3) cardiac or kidney death, kidney failure, hospitalization for heart failure, or sustained doubling in serum creatinine from baseline. Cox regression using time-to-first-event analysis and win ratio (WR) using hierarchical order of events were applied. Empagliflozin reduced the risk of all cardio/kidney composites. The results varied only slightly between Cox and WR (eg, composite 1: hazard ratio, 0.56 [95% CI, 0.49-0.64]; WR, 1.76 [95% CI, 1.53-2.02]. WR prioritizes events by clinical importance; in particular, all fatal events are evaluated, whereas Cox regression ignores deaths when preceded by nonfatal events. Of the 285 cardio/kidney deaths in the analysis, 44 to 56 (15%-20%), depending on the composite, occurred after a nonfatal event and were not evaluated in Cox regression but evaluated by the WR. CONCLUSIONS; By considering the clinical relevance of different event types, the WR represents an appropriate method to complement the traditional time-to-first-event analysis in cardio/kidney outcomes.