The COMET Initiative database: progress and activities from 2011 to 2013.

The Core Outcome Measures in Effectiveness Trials (COMET) Initiative database is an international repository of studies relevant to the development of core outcome sets. By the end of 2013, it included a unique collection of 306 studies. The website is increasingly being used, with more than 12,000 visits in 2013 (a 55% increase over 2012), 8,369 unique visitors (a 53% increase) and 6,844 new visitors (a 48% increase). There has been a rise in visits from outside the United Kingdom, with 2,405 such visits in 2013 (30% of all visits). By December 2013, a total of 4,205 searches had been completed, with 2,139 in 2013 alone.