Reporting a systematic review.

The main purpose of an abstract is to summarize the key elements of a paper so that the reader can decide whether to read the full text or not. Abstracts should be stand-alone documents. Authors need to be aware that the abstract may be the only part of the paper available to many readers, and should therefore provide a balanced presentation of the review content. 9 Neither links to other parts of the review nor trade names nor nonstandard unexplained abbreviations should appear in the abstract. 27 Both the PRISMA Explanation Document and the Cochrane Handbook include sample abstracts (a proposal for a structure following PRISMA is included in Table 2 ).