SYSTEMATIC REVIEW OF THE ASSESSMENT OF PUBLICATION BIAS IN EARLY CASGEVY INTERVENTION IN RANDOMIZED CONTROLLED TRIALS

Abstract

Background: The increased use of meta-analysis in systematic reviews of healthcare interventions has highlighted several types of bias that can arise during the completion of a randomized controlled trial. Study publication bias has been recognized as a potential threat to the validity of meta-analysis and can make the readily available evidence unreliable for decision making. Until recently, outcome reporting bias has received less attention. 

Methodology: We review and summarize the evidence from a series of cohort studies that have assessed study publication bias and outcome reporting bias in randomized controlled trials. Nineteen studies were eligible all the way through from protocol approval to information regarding publication of outcomes. 

Principal Findings: Eight of the studies investigated study publication bias and ten studies have found that statistically significant outcomes had a higher risk of being fully reported compared to non-significant outcomes (range of risk ratios: 1.9 to 3.4). In comparing trial publications to protocols, we found that 40–65% of studies had at least one primary outcome that was changed, introduced, or omitted. We decided not to undertake meta-analysis due to the differences between studies. 

1. Conclusions: Recent work provides direct empirical evidence for the existence of study publication bias and outcome reporting bias. There is strong evidence of an association between significant results and publication; studies that report positive or significant results are more likely to be published and outcomes that are statistically significant have higher risk of being fully reported. Publications have been found to be inconsistent with their protocols. Researchers need to be aware of the problems of both types of bias and efforts should be concentrated on improving the reporting of trials.