Once you have finished searching and deduplicated your results, it is time to screen and select your studies.
There are two stages in the screening process.
Review the titles and abstracts of all studies to remove the obviously irrelevant studies. At least 3 reviewers are needed for this step. 2 reviewers to screen results independently and a third as a tiebreaker.
Retrieve the full-text of the potentially relevant studies and review the full-text against your predefined eligibility criteria. Where appropriate correspond with authors to clarify study eligibility.
For more detailed guidance on the screening/selection process see the Cochrane Handbook chapter on selecting studies: