The COMPare Trials Project

Picture1Trials are routinely misreported: their prespecified outcomes are switched between registration, and publication. This leads to reporting bias. How can we hold individual authors and journals accountable?

The COMPare (CEBM Outcome Monitoring Project) team is monitoring clinical trials for switched outcomes. Through increased awareness of misreported outcomes, individual accountability, and feedback for specific journals, we hope to fix the ongoing problem of outcome switching.

Why outcome switching matters

Before carrying out a clinical trial, all outcomes that will be measured (e.g. blood pressure after one year of treatment) should be pre-specified in a trial protocol, and on a clinical trial registry.

This is because if researchers measure lots of things, some of those things are likely to give a positive result by random chance (a false positive). A pre-specified outcome is much less likely to give a false-positive result.

Once the trial is complete, the trial report should then report all pre-specified outcomes. Where reported outcomes differ from those pre-specified, this must be declared in the report, along with an explanation of the timing and reason for the change. This ensures a fair picture of the trial results.

However, in reality, pre-specified outcomes are often left unreported, while outcomes that were not pre-specified are reported, without being declared as novel. This is an extremely common problem that distorts the evidence we use to make real-world clinical decisions.

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