Article type
Year
Abstract
Background: The rigorous requirements for each step of a systematic review are detailed in the Cochrane Handbook. For instance, there must be two independent reviewers to screen the eligible studies and extract the data. Furthermore, the Handbook states that trials registries should be searched for each Cochrane Review. To date, there are more 20 international trial registries, such as the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP), ClinicalTrials.gov, etc. However, is it really significant to search trial registries for systematic reviews?
Objectives: To investigate the searching of trial registries in Cochrane Reviews and analyze whether this activity changes the results of the reviews.
Methods: We sampled Cochrane Reviews published in 2013. Two reviewers extracted the data independently. The extracted data included whether a trial registry had been searched, the number and name of the trial registries, the trials included in reviews, and whether the researchers could access the data, etc. We assessed the impact of studies from trial registries for the pooled effect size of the reviews through sensitivity analyses.
Results: A total of 992 Cochrane Reviews were published in 2013. Of those, 974 (98.2%) had searched the registries (mean = 2, range: 1-20). The top five most frequently searched registers were the Cochrane Group Register (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 studies from registries. Of those, nine (1%) reviews synthesized the data from studies obtained from registries. 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 search trial registries, and a small number of reviews include the studies from registries. However, few reviews’ results are affected by the studies from registries.
Objectives: To investigate the searching of trial registries in Cochrane Reviews and analyze whether this activity changes the results of the reviews.
Methods: We sampled Cochrane Reviews published in 2013. Two reviewers extracted the data independently. The extracted data included whether a trial registry had been searched, the number and name of the trial registries, the trials included in reviews, and whether the researchers could access the data, etc. We assessed the impact of studies from trial registries for the pooled effect size of the reviews through sensitivity analyses.
Results: A total of 992 Cochrane Reviews were published in 2013. Of those, 974 (98.2%) had searched the registries (mean = 2, range: 1-20). The top five most frequently searched registers were the Cochrane Group Register (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 studies from registries. Of those, nine (1%) reviews synthesized the data from studies obtained from registries. 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 search trial registries, and a small number of reviews include the studies from registries. However, few reviews’ results are affected by the studies from registries.