Acquire (A-2): search for evidence

A comprehensive electronic literature search was conducted to retrieve the relevant evidence published before and including July 2015. Three databases were used for a formal literature search: PubMed, CINAHL, and EMBASE (focusing on international biomedical literature). Details of the formal literature search strategy can be found in Supplemental Appendix C (see the online Data Supplement). In addition, the systematic review team used other sources to locate relevant studies including hand searches (e.g., the citations from retrieved studies, Google scholar) and referrals from the experts in the field (e.g., expert panel team). To collect relevant unpublished data, researchers in the field, laboratories, and institutions were invited through personal requests and the LMBP website, but the review team did not receive any relevant unpublished data to be included in this review.