Impact of selective reporting bias on stroke trials: potential compromise in evidence synthesis - A cross-sectional study.

Background: Accurate reporting of outcomes is crucial for interpreting the results of randomized controlled trials (RCTs). However, selectively reporting outcomes in publications to achieve researchers' anticipated results still occurs frequently. This study aims to investigate the prevalence of selective reporting of outcomes in RCTs on treating acute ischemic stroke (AIS), identify factors contributing to this issue, and assess its potential impact on the degree and direction of intervention effect.

Methods: A search was conducted in MEDLINE, Embase, and the Cochrane Library to collect interventional RCTs on AIS published from 2020 to 2022. Full texts of RCTs were reviewed, and only those reporting International Clinical Trials Registry Platform primary registry numbers were included. Registration information of the RCTs was extracted from the registry platforms and compared with the publications' details to assess the selective reporting of outcomes. Bayesian multilevel logistic regression was used to analyze the reasons behind selective reporting.

Results: Among the total of 159 AIS RCTs identified, 82 (51.6%) were ultimately included, as they reported registration numbers, which encompassed 819 outcomes. Among them, 72 RCTs (87.8%) and 497 outcomes (60.7%) exhibited selective reporting. Omission-type selective reporting (downgrading, omitting, or ambiguously reporting) accounted for 36.4%, while addition-type selective reporting (upgrading, adding, or altering the measurement scope of outcomes) comprised 63.6%. Omission-type selective reporting correlated with negative results (OR: 7.39; 95% CI: 4.08-13.44), whereas addition-type selective reporting correlated with positive results (OR: 2.07; 95% CI: 1.34-3.26) and publication in journals that are not in the top quartile of the Journal Citation Reports (OR: 2.48; 95% CI: 1.15-5.38).

Conclusions: Registered interventional AIS RCTs still face significant issues regarding selective reporting of outcomes. Therefore, it is necessary to further evaluate the influence of selective reporting bias on the positive results obtained from individual AIS RCTs and the systematic reviews based on these RCTs.