Dr. Savva raises an important question. Systematic reviews can now be registered, just like clinical trials and we support this effort. Unfortunately we were not aware of registration services when we began our analysis in the fall of 2011. We later learned about the Prospero system (see http://www.crd.york.ac.uk...). Although the system was apparently developed in 2011, and a preliminary report was published in 2013(1), the founding principles were not released until May of 2014 (http://www.crd.york.ac.uk...). We do support registration of reviews and would have used this service had we been aware of it when we began our work. We recognize that registration reduces biases, promotes transparency of methods and avoids potential duplication. To facilitate the replication of our our work by others, the tables in the paper and the detailed online Supplemental Materials report the PRISMA diagram, the number of results returned and excluded, and raw numbers and RR used in calculations. We support replication and encourage others to reproduce our findings. However, we agree with Dr. Savva that not preregistering the study should have been listed as a limitation of our analysis.

1. Booth A. PROSPERO’s progress and activities 2012/13. Systematic reviews 2013;2:111.