The effect of the CONSORT statement on the amount of "unclear" Risk of Bias reporting in Cochrane Systematic Reviews.

Background The Consolidated Standards of Reporting Trials (CONSORT) statement aims to improve clarity and consistency of transparency of reporting in Randomized Controlled Trials (RCTs). The Cochrane Risk of Bias (RoB) tool for RCTs helps authors to judge the RoB. as ''low", "high" or "unclear". Objective In this study we aimed to assess whether the implementation and updates of the CONSORT statement influenced the trend of "unclear" RoB scores of RCTs included in Cochrane systematic reviews. Methods All Cochrane reviews published in December to October 2016 were retrieved. The publication year of RCTS included in the reviews were sorted into time frames (≤1995, 1996-2000, 2001-2009 and ≥2010) based on the release- and updates of the CONSORT statement (1996, 2001 and 2010). The association between "unclear" RoB versus "low or high" RoB and the year of publication in different time frames were calculated using a binary logistic regression. Results Data was extracted from 64 Cochrane reviews, with 989 RCTS (6471 items). The logistic regression showed that the odds of RCTs published ≥2010, compared to ≤1995 were more likely not to report an "unclear" RoB for the total data (Odds Ratio (OR) 0.69 (95% Confidence interval: 0.59-0.80)), random sequence generation (OR 0.32 (0.22-0.47), allocation concealment (0.64 (0.43-0.95)) and incomplete outcome data (OR 0.60 (0.39-0.91)). Conclusion A slight decrease of "unclear" RoB reporting over time was found. To improve quality of reporting authors are encouraged to adhere to reporting guidelines.