Survey of outcomes in Cochrane Reviews: support for ‘core outcome set’ (COS) development

Article type
Authors
Smith V1, Clarke M2, Williamson P3, Gargon E3
1Trinity College Dublin, Ireland
2Queens University Belfast, Northern ireland
3University of Liverpool, UK
Abstract
Background:
Many systematic reviewers encounter difficulties when synthesising evidence from individual studies because of heterogeneity in the outcomes measured in those studies. Developing and applying agreed standardized sets of outcomes, known as ‘core outcome sets’ (COS), would help overcome this through more consistency in the measurement and reporting of outcomes in trials. COS might also make reviews more useful to decision makers. The Core Outcome Measures in Effectiveness Trials initiative (COMET) has been helping since 2010, by facilitating the development and use of COS and is developing a strategy to assist Cochrane Review Groups (CRGs) wishing to make more use of COS.

Objectives:
To describe the variety of outcomes used in Cochrane Reviews, which were published in full for the first time in 2007 or 2011.

Methods:
We did a descriptive survey of new Cochrane Reviews from 2007 and 2011, by extracting information on the outcomes specified in the methods section and reported in the results section of each review. Numbers, types and frequencies of similar outcomes were identified across reviews.

Results:
We included 788 reviews, specifying 6127 outcomes. After excluding outcomes that had been specified in the 86 reviews that did not include any studies, we found that 1996 (37%) outcomes were not reported. The median number of specified outcomes per review was 7. Of the 2011 reviews that included studies, 361 (31%) published a ‘Summary of Findings’ table (SoF). Of these SoFs, 27% included the recommended maximum of 7 outcomes. Fifteen broad outcome categories were used to manage the outcome data during data extraction and analyses. There was consistency in use of these categories across CRGs, but inconsistency in outcomes and outcome measurement within the categories.

Conclusions:
Further work on COS will make it easier for the results of studies to be compared, contrasted and combined, as appropriate. This will reduce waste in research and produce more informed decisions about care.