Results from the searches will be imported into EndNote bibliographic software and duplicates removed. The titles and abstracts of publications obtained by the search strategy will be independently screened by two authors . Articles that do not meet the inclusion criteria will be removed. All remaining publications will be retrieved for further assessment. Based on the information within the full reports, two review authors will use a standardised form tested prior to use to select the trials eligible for inclusion in the review, if necessary, a third review author will resolve disagreements. A record will be kept of all articles excluded at this stage and the reason for their exclusion.
No language restrictions will be made; non-English papers will be assessed and, if necessary, translated with the assistance of a native speaker.