Monday, 6 October 2014

Is there bias in systematic reviews?

School of Public Health PhD student, Matthew Page has co authored a study which has found that discrepant outcome reporting between the protocol and published systematic review is fairly common, although the association between statistical significance and discrepant outcome reporting is uncertain.

According to the study, a systematic review summarises evidence from multiple studies to answer a specific research question (e.g. what are the benefits and harms of a particular intervention for a particular health condition?). Often, there are many outcomes that systematic review authors could report to address their research question and many different results available for a particular outcome. 

If the decision about which outcomes to investigate in a systematic review is made based on the results for those outcomes in the eligible studies, this may lead to bias. While, if the decision about which outcomes to report in a systematic review and the ways to report them is based on the results, this may mislead users of the systematic review.
The study found that outcomes investigated and reported in systematic reviews were often changed between the protocol and published systematic review. It also found that it was unclear whether the decision to make these changes was related to how statistically convincing the treatment effect for that outcome was. 

Click here to read the full study.

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