Established search filters may miss studies when identifying randomized controlled trials

Abstract

Objectives: The authors were becoming increasingly aware of studies reporting randomized controlled trial (RCT), which reported trial phase but did not mention study design or randomization in the title or abstract. The objective of this study was to determine if established RCT literature search filters should include terms for trial phase.

Study design and setting: This study is a case study. A search filter for trial phase (the P3 filter) was developed, and its sensitivity, efficiency, and value were determined when compared with two established RCT literature search filters (The Cochrane Highly Sensitive Search Strategies [HSSS] and the Royle and Waugh Brief RCT Search Strategy [BRSS]) in the year 2015-improved sensitivity was determined where the P3 filter identified studies missed by either of the established filters; efficiency was determined by the number needed to read; and the Cochrane risk of bias tool was used to determine study quality as a proxy for value.

Results: Both established filters missed studies. The HSSS missed one RCT and four follow-up RCT studies. The BRSS missed one RCT and five follow-up RCT studies. Study quality was unclear.

Conclusion: Established RCT literature search filters may miss studies where trial phase is reported instead of terms for study design or randomization. The P3 filter can be incorporated to improve sensitivity.

Keywords: Literature search effectiveness; Literature searching; RCT; Randomised controlled trials; Search filters; Systematic reviews.