How to avoid missing half the evidence when conducting systematic reviews
posted on: Jul 4, 2012
A new study highlights the importance of electronic literature searches by demonstrating how different search strategies can affect the conclusions of a systematic review.
Literature searching has a vital role to play in evidence-informed policy and practice, and it is plausible to theorise a direct pathway by which poor searches may lead to reviews that make erroneous conclusions based on incomplete evidence. If erroneous findings then influence practice, this could result in decisions that waste resources and, possibly, cause direct harm.
The study, recently published in BMJOpen, compares the results of two electronic literature searches for a systematic review: one included search terms for a range of specific health conditions, while the other included only generic terms for health and illness. We found that both searches were necessary because each identified around half the studies that were included in the final review. Furthermore, each search uniquely identified some of the review's more robust studies. The two searches also identified studies that use different health outcome measures. Failure to identify some of those outcomes would have directly affected our review's conclusions.
The authors of the study conclude that conducting research to improve the effectiveness of literature searching should be a priority. By nesting studies within the process of conducting systematic reviews (as this study does), research on literature searching can be conducted with minimal additional resources and can therefore be considered an inexpensive way of conducting useful research in an important field.
Egan M, MacLean A, Sweeting K, et al
. Comparing the effectiveness of using generic and specific search terms in electronic databases to identify health outcomes for a systematic review: a prospective comparative study of literature search methods. BMJ Open