Methodologic quality and risk-of-bias in systematic reviews of healthcare interventions: a review of methods

OBJECTIVE: To compare the characteristics of systematic reviews of healthcare interventions that assessed or did not methodologic quality/risk-of-bias of included studies. Additionally, to analyze methodologic features of those assessing the methodologic quality/risk-of-bias. METHODS: PubMed database was searched. From 25,571 systematic reviews retrieved, a random sample of 1,025 was screened. Frequencies were used to describe outcomes. Unadjusted and adjusted logistic regressions were performed to test the associations with methodologic quality/risk-of-bias results assessment. In a second analysis, systematic reviews that assessed methodologic quality/risk of bias were dichotomized according to the design of included studies (randomized clinical trials-only versus non-randomized studies of intervention or a combination of both). RESULTS: 303 systematic reviews were fully analyzed. Methodologic quality/risk of bias was assessed by 278 (92%). Methodologic quality/risk-of-bias assessment was associated with a higher number of databases searched (>4, P= 0.008), the presence of meta-analysis (P= 0.005), and the design of included studies (randomized clinical trials-only, P= 0.042). The chance of using a suitable tool and a tool designed for risk-of-bias assessment rather than methodologic quality was higher for randomized clinical trials-only systematic reviews (P< 0.05). The most used tool was Cochrane’s RoB Tool without a clear studies’ overall risk classification system. CONCLUSION: methodologic quality/risk-of-bias assessment was associated with included studies’ design (randomized clinical trials-only), a meta-analysis of data, and the number of databases searched (>4). The most used tool was Cochrane’s RoB Tool, with no clearly defined rating system. Methodologic quality/risk-of-bias assessment methods description, results, and impacts on meta-analysis, the certainty of evidence, and systematic reviews’ results are still to be consistently addressed.