Harms of outcome switching in reports of randomised trials: CONSORT perspective

Rigorous and transparent conduct of clinical trials is essential for confidence in their results. Randomised trials must have a protocol that gives details of the planned study design and outlines the intended methods of analysis, reflecting substantial discussions among the investigators. Key elements of the study design should also be included in an entry on a clinical trials registry. The core principles, as set out in the SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) statement,1 are that the protocol should give full details about objectives and planned conduct; the protocol should be adhered to; and any changes from what was initially planned should be reported and, ideally, explained. The SPIRIT guidance for protocols intentionally overlaps considerably with CONSORT recommendations for what information should be included in the report of a randomised trial.2

A particular concern is that researchers should specify the primary and secondary outcomes that will be assessed, including the method and timing of measurement. When the trial’s findings are published, the main reported results should be for those predeclared outcomes and any differences should be highlighted and explained. Adherence to a prespecified plan avoids bias, gives credibility to the results, and avoids confusion for the reader. Conversely, when authors substitute other outcomes after the trial has started there must be concern that such changes were done with knowledge of the data. That casts doubt on the reliability and integrity of the results.