Using the full PICO model as a search tool for systematic reviews resulted in lower recall for some PICO elements

Objectives: The use of the four-part PICO model to facilitate search strategy development for a precise answer is recommended for structuring searches for systematic reviews. Existing guidelines generally recommend that a search strategy should include the population, intervention(s), and types of study design. Consequently, comparison and outcome are not recommended as a part of the search strategy. There is evidence that comparison and particularly outcome is not represented in enough detail, but this needs to be confirmed. Study Design and Setting: The present study examines the presence of PICO elements in the records in two commonly used databases for health sciences research: Embase and PubMed. We examine the field of upper GI and pancreatic diseases as well as the field of pregnancy and childbirth by extracting the included studies as well as the related PICO elements from a random selection of Cochrane reviews within these two areas. Results: We find that the PICO elements C and O had a lower retrieval potential across the two Cochrane groups and databases also when combining text words and subject headings. In particular, we find a lower retrieval when searching for both primary and secondary outcomes. Conclusion: Our results support the existing recommendation not to search for outcomes.