Abstract: Fifty-three publications reporting 50 evaluations were included. The total number of RCTs assessed within evaluations was 16,604 (median per evaluation 123 (interquartile range (IQR) 77 to 226) published in a median of six (IQR 3 to 26) journals. Characteristics of the included RCT populations were variable, resulting in heterogeneity between included evaluations. Validity assessments of included studies resulted in largely unclear judgements. The included evaluations are not RCTs and less than 8% (4/53) of the evaluations reported adjusting for potential confounding factors. Twenty-five of 27 outcomes assessing completeness of reporting in RCTs appeared to favour CONSORT-endorsing journals over non-endorsers, of which five were statistically significant. 'Allocation concealment' resulted in the largest effect, with risk ratio (RR) 1.81 (99% confidence interval (CI) 1.25 to 2.61), suggesting that 81% more RCTs published in CONSORT-endorsing journals adequately describe allocation concealment compared to those published in non-endorsing journals. Allocation concealment was reported adequately in 45% (393/876) of RCTs in CONSORT-endorsing journals and in 22% (329/1520) of RCTs in non-endorsing journals. Other outcomes with results that were significant include: scientific rationale and background in the 'Introduction' (RR 1.07, 99% CI 1.01 to 1.14); 'sample size' (RR 1.61, 99% CI 1.13 to 2.29); method used for 'sequence generation' (RR 1.59, 99% CI 1.38 to 1.84); and an aggregate score over reported CONSORT items, 'total sum score' (standardised mean difference (SMD) 0.68 (99% CI 0.38 to 0.98)). Evidence has accumulated to suggest that the reporting of RCTs remains sub-optimal. This review updates a previous systematic review of eight evaluations. The findings of this review are similar to those from the original review and demonstrate that, despite the general inadequacies of reporting of RCTs, journal endorsement of the CONSORT Statement may beneficially influence the completeness of reporting of trials published in medical journals. Future prospective studies are needed to explore the influence of the CONSORT Statement dependent on the extent of editorial policies to ensure adherence to CONSORT guidance.

Plain-language summary: A group of experts has developed a checklist and flow diagram called the CONSORT Statement. The checklist is designed to help authors in the reporting of randomised controlled trials (RCTs). This systematic review aims to determine whether the CONSORT Statement has made a difference to the completeness of reporting of RCTs. Reporting of RCTs published in journals that encourage authors to use the CONSORT Statement with those that do not is compared. We found that some items in the CONSORT Statement were fully reported more often when journals encouraged the use of CONSORT. While the majority of items are reported more often when journals endorse CONSORT, the data only showed a statistically significant improvement in reporting for five of 27 items. No items suggest that CONSORT decreases the completeness of reporting of RCTs published in medical journals. None of the evaluations included in this review used experimental designs, and their methodological approaches were mostly poorly described and variable when they were described. Furthermore, evaluations assessed the completeness of reporting of RCTs within a wide range of medical fields and in journals with a wide variation in the enforcement of CONSORT endorsement. Our results do have some limitations, but given the number of included evaluations and the number of assessed RCTs, we conclude that while most RCTs are incompletely reported, the CONSORT Statement beneficially influences their reporting quality.