Statistical analysis plan for the Standard versus Accelerated Initiation of Renal Replacement Therapy in Acute Kidney Injury (STARRT-AKI) trial

Background: The Standard versus Accelerated Initiation of Renal Replacement Therapy in Acute Kidney Injury (STARRT-AKI) trial is a multinational randomised controlled trial that will enrol a minimum of 2866 patients comparing two strategies for initiating renal replacement therapy in critically ill patients with acute kidney injury. Objective: To describe a pre-specified statistical analysis plan (SAP) for the STARRT-AKI trial before completion of patient recruitment and data collection. Methods: The SAP was designed by the principal investigators and statisticians and approved by the international STARRT-AKI Steering Committee. The primary and secondary outcomes are defined, the approach to safety monitoring and data collection are summarised, and a detailed description of the planned statistical analyses, including pre-specified subgroup and secondary analyses, is described. Results: We have developed the SAP for the STARRT-AKI trial, including a mock CONSORT diagram, figures and tables. The primary outcome is 90-day all-cause mortality. The primary analysis will be reported as a relative risk (95% CI), absolute risk difference (95% CI), and tested with the 'X'2 test. Secondary analyses of the primary outcome will include adjustment for baseline covariates and site, and evaluation for heterogeneity in treatment effect. Pre-specified subgroups will include patient sex, baseline kidney function, illness acuity, surgical status, presence of sepsis, and geographic location. Conclusion: To align with best practice standards for rigour, internal validity and transparency, we have developed a SAP for the STARRT-AKI trial before trial completion. The analysis will adhere to the SAP to avoid bias arising from knowledge of trial results.