Moher D. The problem of duplicate systematic reviews. BMJ 2013;347:f5040
Two or three systematic reviews on the same topic are usually considered reasonable. But, when does replication become unnecessary duplication? The best way to reduce unnecessary duplication of systematic reviews may be to make it compulsory for reviewers to identify existing reviews, either protocols or completed reviews, before conducting their own review. PROSPERO is an international prospective register that can be used to search for existing systematic review protocols.