Article type
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Abstract
Background: Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) are given first consideration when including studies for Cochrane reviews. The Cochrane Effective Practice and Organisation of Care Group (EPOC) additionally considers two alternative designs for inclusion in their reviews. Depending on the knowledge and expertise of the author and the editorial board, EPOC reviews can include RCTs, CCTs and controlled before after studies (CBAs) as well as interrupted time series studies (ITSs). The impact of including the additional designs is not known.
Objective: The objective of this study is to report the frequency of each study design included in EPOC reviews.
Methods: Data were collected from the included studies of EPOC reviews in The Cochrane Library, Issue 1, 2005. Withdrawn reviews were excluded from the analysis. The number of included studies per review were categorized by study design.
Results: Thirty-two EPOC Cochrane reviews were available for the analysis with a total of 566 included studies. There were 459 RCTs (81%), 11 CCTs (2%), 65 CBAs (12%) and 31 ITSs (5%). Three reviews did not have included studies. Eight reviews defined their inclusion criteria as only RCTs with a total of 205 RCTs. In the 24 reviews that included additional designs, there were 254 RCTs (70%) and the CCTs, CBAs and ITSs accounted for 3%, 9% and 18% of the studies in this subgroup respectively. One study found no RCTs, but included 20 studies of other designs.
Conclusion: Based on our present reviews, non-RCTs account for less than 20% of the included studies in EPOC reviews. Twenty-five percent of EPOC reviews consider only RCTs for inclusion. Further research is necessary to establish the impact of including non-RCTs in Cochrane reviews.
Objective: The objective of this study is to report the frequency of each study design included in EPOC reviews.
Methods: Data were collected from the included studies of EPOC reviews in The Cochrane Library, Issue 1, 2005. Withdrawn reviews were excluded from the analysis. The number of included studies per review were categorized by study design.
Results: Thirty-two EPOC Cochrane reviews were available for the analysis with a total of 566 included studies. There were 459 RCTs (81%), 11 CCTs (2%), 65 CBAs (12%) and 31 ITSs (5%). Three reviews did not have included studies. Eight reviews defined their inclusion criteria as only RCTs with a total of 205 RCTs. In the 24 reviews that included additional designs, there were 254 RCTs (70%) and the CCTs, CBAs and ITSs accounted for 3%, 9% and 18% of the studies in this subgroup respectively. One study found no RCTs, but included 20 studies of other designs.
Conclusion: Based on our present reviews, non-RCTs account for less than 20% of the included studies in EPOC reviews. Twenty-five percent of EPOC reviews consider only RCTs for inclusion. Further research is necessary to establish the impact of including non-RCTs in Cochrane reviews.