Before any papers are acquired for evaluation, sifting of the search output is carried out to eliminate irrelevant material.
- Papers that are clearly not relevant to the key questions are eliminated based on their title.
- Abstracts of remaining papers are then examined and any that are clearly not appropriate study designs, or that fail to meet specific methodological criteria, will be also eliminated at this stage.
- All reports of studies that are identified as potentially eligible must then be assessed in full text to see whether they meet the inclusion criteria for the review.
The reproducibility of this process should be tested in the initial stages of the review, and if reproducibility is shown to be poor more explicit criteria may have to be developed to improve it.
Authors must decide whether more than one author will assess the relevance of each report. Whatever the case, the number of people assessing the relevance of each report should be stated in the Methods section of the review. Some authors may decide that assessments of relevance should be made by people who are blind or masked to the journal from which the article comes, the authors, the institution, and the magnitude and direction of the results by editing copies of the articles (Berlin 1997; Berlin, Miles, and Crigliano 1997). However, this takes much time, and may not be warranted given the resources required and the uncertain benefit in terms of protecting against bias (Berlin 1997).