Publication Bias and Selective Outcome Reporting in Randomized Controlled Trials Related to Rehabilitation: A Literature Review.

OBJECTIVE

To investigate the rate of registered protocols published as research papers as a measure of publication bias, and the concordance rates of the primary outcomes between research protocol and published papers as a measure of selective outcome reporting bias in randomized controlled trials (RCTs) related to rehabilitation.

DATA SOURCES

Protocols related to RCTs were extracted from electronic databases, the University Hospital Medical Information Network (UMIN), International Standard Research Clinical Trial Number (ISRCTN), ClinicalTrials.gov, and MEDLINE. Published papers were retrieved from MEDLINE.

STUDY SELECTION

The inclusion criteria were as follows: (1) initial registration (UMIN, ISRCTN, ClinicalTrials.gov) within the designated period; (2) published as a paper from a research protocol in MEDLINE (PubMed); and (3) written in English or Japanese. The search period was from January 1, 2013, to December 31, 2020.

DATA EXTRACTION

The outcome of this study was set as the rate of published papers that were consistent with the extracted research protocol and the concordance rate between the primary outcomes in published papers and in protocols. The concordance rate of the primary outcomes was evaluated by checking whether the description in the research protocol matched that in the paper's abstract and main text.

DATA SYNTHESIS

Out of the 5597 research protocols registered, only 727 were published (13.0%). The concordance rates of the primary outcomes were 48.7% and 72.6% in the abstract and main text, respectively.

CONCLUSIONS

This study revealed major discrepancies between the number of research protocols and published papers, and difference of description regarding the primary outcomes in published papers which were already defined in the research protocols.