Searching clinical trial registries in interventional physical therapy systematic reviews: A Pilot Cross-sectional Analysis

Background. Studies with positive findings are more likely to be published compared to those with negative findings. Therefore the latter studies are often disregarded in systematic reviews. This causes an overestimation of a treatment effect size which leads to a misinterpretation of the evidence. Searching clinical trial registries in systematic reviews is a useful source to retrieve unpublished clinical trials leading to the reduction of publication bias. Previous studies in the literature reported inconsistent searching of clinical trial registries in systematic reviews published in several medical fields. Searching clinical trial registries in physical therapy is still unknown. The aim of this cross-sectional analysis is to evaluate the extent of clinical trial registry searching in physical therapy interventional systematic reviews.

Methods. Systematic reviews published between January 2017 and January 2018 were retrieved from five reputable physical therapy journals. Interventional systematic reviews that were coherent with the inclusion criteria were included in the analysis.

Results. The search yielded 40 systematic reviews. Among these 19 were interventional systematic reviews as well as being consistent with the inclusion criteria and thus were considered for the analysis. After reviewing their search methodology, only two reviews (10.5%) reported searching at least one clinical trial registry.

Discussion. The results of this study suggest poor searching of clinical trial registries in physical therapy systematic reviews. Due to the limitations of this study, further research analyzing large samples of interventional physical therapy systematic reviews is required.