Lessons for search strategies from a systematic review, in The Cochrane Library, of nutritional supplementation trials in patients after hip fracture

Background: A key aim when conducting systematic reviews of randomized controlled trials (RCTs) is to include all of the evidence, if possible. Serious bias may result if trials are missed through inadequate search strategies.

Objective: The objective was to evaluate the search plan for identifying RCTs in nutrition as part of a systematic review, in The Cochrane Library, of nutritional supplementation trials in patients after hip fracture.

Design: We identified potential studies by searching the electronic databases BIOSIS, CABNAR, CINAHL, EMBASE, HEALTHSTAR, and MEDLINE; reference lists in trial reports; and other relevant articles. We also contacted investigators and other experts for information and searched 4 nutrition journals by hand.

Results: We identified 15 RCTs that met the predefined inclusion criteria. The search plan identified 8 trials each in EMBASE, HEALTHSTAR, and MEDLINE and 7 in BIOSIS and CABNAR. BIOSIS was the only electronic database source of 2 trials. Eleven trials were identified by searching electronic databases and 2 unpublished trials were identified via experts in the field. We found one trial, published only as a conference abstract, by searching nutrition journals by hand. After publication of the protocol for the review in The Cochrane Library, we were informed of another unpublished trial.

Conclusions: We found that a limited search plan based on only MEDLINE or one of the other commonly available databases would have failed to locate nearly one-half of the studies. To protect against bias, the search plan for a systematic review of nutritional interventions should be comprehensive.