Competing interests: We have read and understood the BMJ Group policy on declaration of interests and declare the following: all authors are convenors or members of the Cochrane PMA Methods Group and have been involved in numerous prospective meta-analyses. LA, DG, and JAB have published several methods articles on prospective meta-analyses and are authors of the prospective meta-analysis chapter in the Cochrane Handbook for Systematic Reviews of Interventions. LA manages the Australian New Zealand Clinical Trials Registry (ANZCTR). ALS and KEH work for the ANZCTR. JAB is a full time employee of Johnson & Johnson.