A systematic review of trends in the methodological quality of randomized controlled trials in various research fields

Objectives: We sought to evaluate the trends in the methodological quality of randomized controlled trials in various medical fields. Study Design and Setting: Relevant studies were retrieved by the PubMed and the ISI Web of science databases. Results: Thirty-five out of 457 retrieved studies met the inclusion criteria. Twenty-one out of 35 selected studies reported significant improvement in at least one methodological quality factor. Overall quality scores were increased in 13 out of 26 studies providing relevant data. The most commonly separately examined key quality factors were allocation concealment and blinding in 13 out of 21 studies that reported relevant data. Allocation concealment was the quality characteristic most commonly reported as significantly improving during the reviewed period (in five out of eight studies reporting relevant comparative data). Conclusion: Certain aspects of methodological quality have improved significantly over time, but others remain stagnant. Further efforts to improve study design, conduct, and reporting of randomized controlled trials are warranted. (C) 2008 Elsevier Inc. All rights reserved.