Hierarchical endpoints in critical care: A post-hoc exploratory analysis of the standard versus accelerated initiation of renal-replacement therapy in acute kidney injury and the intensity of continuous renal-replacement therapy in critically ill patients trials

Purpose: To perform a post-hoc reanalysis of the Standard versus Accelerated Initiation of Renal-Replacement Therapy in Acute Kidney Injury (STARRT-AKI) and the Intensity of Continuous Renal-Replacement Therapy in Critically Ill Patients (RENAL) trials through hierarchical composite endpoint analysis using win ratio (WR). Material and methods: All patients with complete information from the STARRT-AKI (which compared accelerated versus standard approaches for renal replacement therapy – RRT initiation) and RENAL (which compared two different RRT doses in critically ill patients) trials were selected. WR was defined as a hierarchical composite endpoint using 90-day mortality, RRT dependency at 90-days, intensive care unit (ICU) length-of-stay (LOS), and hospital LOS (primary analysis); values above the unit represent a benefit of the intervention for the hierarchical composite endpoint. A secondary analysis replacing LOS by days alive and free of RRT was performed. Stratified analyses were performed according to illness severity score, surgical status, and the presence of sepsis. Results: The WR analysis produced 2,141,830 pairs for the STARRT-AKI trial and 536,446 pairs for the RENAL trial, respectively. The WR results for STARRT-AKI and RENAL were 1.04 (95% confidence interval [CI] 0.96–1.13; p = 0.33) and 1.02 (95% CI; 0.90–1.15; p = 0.75) for the primary analysis, and 0.88 (95% CI; 0.79–0.99; p = 0.03) and 1.02 (95% CI; 0.87–1.21; p = 0.77) for the secondary analysis, respectively. The stratified analysis of the primary suggested possible benefit of the accelerated-strategy in the STARRT-AKI trial for non-surgical patients with sepsis, while the secondary analysis suggested possible harm of the accelerated-strategy for surgical patients without sepsis. There was no evidence of heterogeneity in treatment effects in stratified analyses in the RENAL trial. Conclusion: WR approach using a hierarchical composite endpoint is feasible for trials in critical care nephrology. The primary re-analyses of the STARRT-AKI and RENAL trials both yielded neutral results; however, there was suggestion of heterogeneity in treatment effect in stratified analyses of the STARRT-AKI trial by surgical status and sepsis. Selection of the endpoints and hierarchical ordering before trial design using the WR approach can have important implications for trial interpretation. Trial Registry: ClinicalTrials.gov number NCT02568722 (STARRT-AKI) and NCT00076219 (RENAL).