The Unknown Prevalence of Postrandomization Bias in 15 Physical Therapy Journals: A Methods Review.

Objectives: To determine the prevalence of prospective clinical trial registration and postrandomization bias in published musculoskeletal physical therapy randomized clinical trials (RCTs).

Design: A methods review.

Literature Search: Articles indexed in MEDLINE and published between January 2016 and July 2020 were included.

Study Selection Criteria: Two independent blinded reviewers identified the RCTs using Covidence. We included RCTs related to musculoskeletal interventions that were published in International Society of Physiotherapy Journal Editors member journals.

Data Synthesis: Data were extracted independently for the variables of interest from the identified RCTs by 2 blinded reviewers. The data were presented descriptively or in frequency tables.

Results: One hundred thirty-eight RCTs were identified. One third of RCTs were consistent with their prospectively registered intent (49/138); consistency with prospectively registered intent could not be determined for two thirds (89/138) of the RCTs. Four RCTs (8%)reported inconsistent results with the primary aims and 7 (14%) with the outcomes from the prospective clinical trial registry, despite high methodological quality (Physiotherapy Evidence Database [PEDro] scale score). Differences between prospectively registered and non-prospectively registered RCTs for PEDro scale scores had a medium effect size ( = 0.30). Two of 15 journals followed their clinical trial registration policy 100% of the time; in 1 journal, the published RCTs were consistent with the clinical trial registration.

Conclusion: Postrandomization bias in musculoskeletal physical therapy RCTs could not be ruled out, due to the lack of prospective clinical trial registration and detailed data analysis plans. .