Article type
Year
Abstract
Background: There are rigorous requirements for each step of a systematic review in the Cochrane Handbook for Systematic Reviews of Interventions. For instance, there must be two independent reviewers when screening eligible studies and extracting the data, which supports robust evidence. Furthermore, it suggests that the trial register should be searched for each Cochrane Review. To date, there are more 20 international trial registers, such as the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP), ClinicalTrials.gov, etc. However, is it really significant to search the trial register for systematic review?
Objectives: To investigate the search of trial register in Cochrane Reviews and analyze whether it would change the results of the reviews.
Methods: We sampled the Cochrane Reviews published in 2013. Two reviewers extracted the data independently. The extracted data included whether it had searched trial register, the number and name of trial register, the trials included in reviews, and whether the researchers could achieve the data, etc. We assessed the impact of studies from trial register for the pooled effect size of the reviews through sensitivity analyses.
Results: There were 992 Cochrane reviews published in 2013. Of those, 974 (98.2%) had searched the registers (mean = 2, range: 1 to 20). The top five frequently searched registers were Cochrane Group Registers (91%, 890/974), ClinicalTrials.gov (43%, 423/974), WHO ICTRP (34%, 331/974), CCT (19%, 181/974), and the metaRegister of Controlled Trials (mRCT; 12%, 120/974). Thirty-two (3%) reviews included the studies from registers, and nine (1%) reviews synthesized the data from studies from registers. The results of sensitivity analyses showed only three (0.1%) reviews' pooled effect sizes were affected by the data of those studies.
Conclusions: Most Cochrane Reviews have searched the trial register, and small number of reviews include the studies from registers. However, few reviews’ results are affected by the studies from registers.
Objectives: To investigate the search of trial register in Cochrane Reviews and analyze whether it would change the results of the reviews.
Methods: We sampled the Cochrane Reviews published in 2013. Two reviewers extracted the data independently. The extracted data included whether it had searched trial register, the number and name of trial register, the trials included in reviews, and whether the researchers could achieve the data, etc. We assessed the impact of studies from trial register for the pooled effect size of the reviews through sensitivity analyses.
Results: There were 992 Cochrane reviews published in 2013. Of those, 974 (98.2%) had searched the registers (mean = 2, range: 1 to 20). The top five frequently searched registers were Cochrane Group Registers (91%, 890/974), ClinicalTrials.gov (43%, 423/974), WHO ICTRP (34%, 331/974), CCT (19%, 181/974), and the metaRegister of Controlled Trials (mRCT; 12%, 120/974). Thirty-two (3%) reviews included the studies from registers, and nine (1%) reviews synthesized the data from studies from registers. The results of sensitivity analyses showed only three (0.1%) reviews' pooled effect sizes were affected by the data of those studies.
Conclusions: Most Cochrane Reviews have searched the trial register, and small number of reviews include the studies from registers. However, few reviews’ results are affected by the studies from registers.