Clinical trial registers (or registries) provide a public record of the existence of a clinical trial.
A trial registry record typically includes (but is not limited to):
Trial registry records can help identify and possibly minimize two kids of bias that might be introduced into a synthesis review:
There are many trial registries, and choosing which ones to search heavily depends on your topic.
Trial registries should be searched for systematic reviews depending on the efficacy of interventions, conduct, and reporting guidelines. The Cochrane Handbook recommends searching, at a minimum, the two sources below (click on internet icons for direct link):