We searched MEDLINE, the Cochrane Methodology Register, and the Cochrane Database of Systematic Reviews (limited to reviews) up to September 2009, and EMBASE up to August 2007.
When citing empirical evidence in the E&E, we aimed to reference a systematic review when available.
We used piloted forms to screen and extract data relevant to specific checklist items.
Studies were included if they provided empirical data to support or refute the importance of a given protocol concept.
Proper names of trial personnel have been abbreviated with italicised initials, and any reference numbers cited in the original quoted text are denoted by  to distinguish them from references cited in this E&E paper.
For each checklist item we also strived to provide references to empirical data supporting its relevance, which we identified through a systematic review conducted to inform the content of the SPIRIT checklist.