Objectives is a bullet.
A set of explicit criteria were used for selection of literature. A total of 5621 abstracts and articles were identified by initial searches as potentially relevant to the review. A further 22 references were incorporated into the final version of the review as a result of comments from external experts and referees. Feedback from this panel was read and discussed by the authors of the review and a third version of the review drafted. The final version is a quasi-consensus view from individuals with a wide range of expertise.