The choice of outcomes in systematic reviews of the effects of interventions is crucial, dictating which data are included and analyzed. Full prespecification of outcomes in systematic reviews can reduce the risk of outcome reporting bias but, this issue has not been widely investigated. This study is the first to analyze the nature and specification of outcomes used in Cochrane Wounds (CW) systematic reviews. Adequacy of outcome specification was assessed using a five-element framework of key outcome components: outcome domain, specific measurement, specific metric, method of aggregation, and time points. We identified all CW review titles associated with a protocol published on or before October 1, 2014. We categorized all reported outcome domains and recorded whether they were primary or secondary outcomes. We explored outcome specification for outcome domains reported in 25% or more of the eligible protocols. We included 106 protocols and 126 outcome domains; 24.6% (31/126) domains were used as primary outcomes at least once. Eight domains were reported in ≥25% of protocols: wound healing, quality of life, costs, adverse events, resource use, pain, wound infection, and mortality. Wound healing was the most completely specified outcome domain (median 3; interquartile range [IQR] =1–5) along with resource use (median 3; IQR 2–4). Quality of life (median 1; IQR 1–3), pain (median 1; IQR 1–3), and costs (median 1; IQR 1–4) were the least completely specified outcome domains. Outcomes are frequently poorly prespecified and the elements of metric, aggregation, and time-point are rarely adequately specified. We strongly recommend that reviewers be more vigilant about prespecifying outcomes, using the five-element framework. Better prespecification is likely to improve review quality by reducing bias in data abstraction and analysis, and by reducing subjectivity in the decision of which outcomes to extract; it may also improve outcome specification in clinical trial design and reporting.
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