168 Chapter 6 Quality of the included studies The risk of bias of the uncontrolled studies (n=12), estimated with the NewcastleOttawa scale, is shown in table 1. Overall, the quality of the included uncontrolled studies was poor, mainly due to a low score on the comparability domain due to lack of matching of exposed and non-exposed individuals in the study design and/or a lack of correction for confounders in the analyses. Table 1. Risk of Bias Newcastle-Ottawa Scale (NOS) of uncontrolled studies (n=12) Author Score Selection Score Comparability Score Outcome Conclusion Alexaitis et al. 2014 [27] Poor Amato et al. 2006 [28] - Poor Andersen et al. 2017 [29] Poor Davis et al. 2008 [30] Poor Eskandaria et al. 2018 [31] - Poor Hevener et al. 2016 [32] - - - Poor Link et al. 2016 [33] - - Poor McCue et al. 2004 [34] - Poor Mitchell et al. 2018 (3) - - Poor Sinitsky et al. 2017 [35] - Poor Thakker et al. 2018 [36] - Poor Weddle et al. 2016 [37] - Poor Poor quality; 0 or 1 star in selection domain OR 0 stars in comparability domain OR 0 or 1 stars in outcome/ exposure domain. Fair quality: 2 stars in selection domain AND 1 or 2 stars in comparability domain AND 2 or 3 stars in outcome/exposure domain. Good quality: 3 or 4 stars in selection domain AND 1 or 2 stars in comparability domain AND 2 or 3 stars in outcome/exposure domain. The risk of bias of the controlled studies (n=15), scored with EPOC, showed that nine studies scored low risk on seven of the nine risk of bias criteria (figure 2). For only five studies [41-43, 50, 52], the missing outcomes were unlikely to bias the results. For the other studies, there was an unclear or high risk for missing outcomes that were likely to bias the results [38-40, 44-49, 51]. Three studies did not perform statistical tests for measuring the effect of their de-implementation strategy [9, 28, 36].
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