Stefan Elbers

94 Chapter 4 Sixteen studies provided sufficient data to perform meta-analyses. One of these studies used change scores to control for baseline differences (Manning et al., 2014), whereas the other studies used final value scores of their outcome measures. As both type of scores are not compatible within one calculation of a standardized mean difference, we analysed the comparisons of Manning et al. (2014) separately. The four studies that could not be included in the meta-analyses were presented narratively (Taal et al., 1993; Burckhardt et al., 1994; Dworkin et al., 2002; Hutting et al., 2015). Risk of Bias The risk of bias was low for all studies, except for Asenlof et al. (2005), Taal et al. (1993), Dworkin et al. (2002), Burckhardt et al. (1994), and Von Korff et al. (1998). Table 3 shows all risk of bias assessments. Table 3. Risk of Bias Assessment of Included Studies. Study 1 2 3 4 5 6 Andersen (2015) + + + + + + Arvidsson (2013) + + ? - + + Asenlof (2005) + ? - - + + Burckhardt (1994) ? ? ? - ? + Dworkin (2002) ? ? ? - - + Ersek (2008) + + - ? + + Grønning (2012) + + - + + ? Haas (2005) + + ? + ? + Hutting (2015) + + + + ? ? King (2002) + + + ? + + Knittle (2015) + + - + + ? Lefort (1998) + + + + + + Linton (1997) + + ? + + + Manning (2014) + + + + + + Moore (2000) ? ? + + + + Nicholas (2013) + + + ? + + Stuifbergen (2010) + + + + + + Taal (1993) ? ? ? - + - Taylor (2016) + + - + + + Von Korff (1998) ? ? + + + ? 1: Random sequence allocation; (selection bias) 2: allocation concealment (selection bias); 3: blinding of outcome assessment (detection bias); 4: Incomplete outcome data (attrition bias); 5: Selective reporting (reporting bias); 6: Other bias.