175 Risk of bias assessment Due to anticipated heterogeneity of the studies, no one dedicated methodological quality assessment tool is available. For this reason, the Downs and Black checklist for measuring study quality was adjusted to suit the design of each included article (244). Question 27 of the original Downs and Black checklist was adjusted for all studies. A study was awarded a maximum of one point when a power calculation was done. If a question was not applicable to a study, it did not contribute to the final risk of bias evaluation. If due to missing information in a synthesis resulting from reporting bias a question from the Downs and Black checklist could not be answered, a question was awarded with zero points and put as unable to determine (UTD). Based on the risk of bias assessment, an overall quality score was awarded to the studies based on the percentage of points achieved, see Table 7.1. Table 7.1: Definitions of the overall risk of bias quality scores Percentage (%) Overall quality score Colour code > 90 Excellent ☆ 66.7 – 90 Good ● 50 – 66.7 Fair ● < 50 Poor ● Synthesis methods A narrative approach was used to discuss the data extracted from the included studies. A meta-analysis was not carried out due to the expected heterogeneity of included studies.
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