Search strategy analysis

Table S8 outlines the results of four individual searches in EMBASE, MEDLINE, CINAHL and COMET. Twelve studies (46%) were identified in all four individual searches. Of the 16 studies with the primary aim of developing COS, nine (56%) would have been identified in any single search. One COS study was not identifies in any electronic database search, but was identified in the COMET register.40Despite all 26 included studies being registered with COMET, four studies were not identified in our search, due mainly to falling outside our search parameters.