Cochrane Summaries

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Blinded versus unblinded assessments of risk of bias in studies included in a systematic review

Morissette K, Tricco AC, Horsley T, Chen MH, Moher D
Published Online: 
7 September 2011

When researchers want to answer a question they can use an approach called a systematic review, which is intended to examine all of the studies that have been done in a particular area of interest. When examining and summarizing the literature, researchers are expected to determine which of the studies were well-conducted (i.e. high quality) and those that were not. What we do not know enough about is how researchers should conduct the assessments to determine which studies were of high quality. This is important because if the researcher is aware of certain study characteristics (e.g. what journal the study was published in) they may inadvertently assess the study a certain way. For example, if the author of the study is well-known to the assessor, they may be more likely to assume it is of 'high quality'. Our research examines whether blinding researchers to study characteristics makes a difference when the goal is to summarize the literature. We only found a few studies that reported data relevant to our question. The results from these studies were inconsistent, however, the results suggest that it may not make a difference if quality is appraised under blinded or unblinded conditions during a systematic review.

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