Background: Inconsistent outcome selection and reporting in clinical trials may limit their capacity to inform evidence-based decision making and the ability to combine findings in systematic reviews.
Objectives: To assess the scope and consistency of outcome selection and reporting in trials included in systematic reviews of interventions for patients on chronic haemodialysis.
Methods: The Cochrane Database of Systematic Reviews was searched from 1999 to January 2015 for published systematic reviews of interventions for patients on chronic haemodialysis. The description and frequency of outcomes reported within the source randomised controlled trials were assessed.
Results: The 18 systematic reviews included 282 trials that reported over 518 outcomes. There was considerable heterogeneity among the outcomes reported. Across all trials, 320 outcomes occurred only once, and 198 outcomes were identified twice. The five most common outcome domains were mortality (50 trials, 18%), blood pressure (46 trials, 16%), calcium (44 trials, 16%), parathyroid hormone (41 trials, 15%) and quality of life (39 trials, 14 %). There was considerable variation in how the domains were measured, the time at which they were measured, and the units and threshold changes that defined an outcome. For example, blood pressure was reported as pre-dialysis, post-dialysis, maximum, difference in pre- and post-dialysis, ambulatory, resting, rise, and time to restore.
Conclusions: A wide array of outcomes are reported in trials of interventions in haemodialysis, with large heterogeneity in timing of measurements, units of measure, and threshold changes that define an outcome. This highlights the need for a well-defined set of standardized core outcomes to improve the comparability of trial findings in meta-analysis and to provide greater confidence around treatment decisions for patients undergoing haemodialysis.