Table 2.
For each domain risk of bias is rated as high, unclear or low
| Reference | Random sequence generation (Selection bias) | Allocation concealment (Selection bias) | Blinding of participant and personnel (Performance bias) | Blinding of outcome assessment (Detection bias) | Incomplete outcome data (Attrition bias) | Selective reporting (Reporting bias) | Choice of control groups (Bias in design) |
|---|---|---|---|---|---|---|---|
| Bohn 2015 [20] | Low risk | Unclear risk | Low risk | Low risk | Low risk | Low risk | Low risk |
| Chumpitazi 2015 [22] | Low risk | Low risk | Low risk | Low risk | Low risk | Low risk | High risk |
| de Roest 2013 [33] | No randomised | High risk | High risk | High risk | High risk | High risk | High risk |
| Escobar 2014 [45] | High risk | High risk | High risk | High risk | High risk | High risk | Low risk |
| Gijsbers 2012 [42] | High risk | High risk | High risk | High risk | High risk | High risk | High risk |
| Gomara 2008 [43] | High risk | High risk | High risk | High risk | High risk | High risk | High risk |
| Gremse 2003 [41] | Unclear risk | Unclear risk | High risk | High risk | High risk | High risk | Low risk |
| Halmos 2014 [28] | Low risk | Unclear risk | Low risk | Unclear | Low risk | Low risk | High risk |
| Houstoft 2016 [31] | Low risk | Low risk | Low risk | High risk | Unclear | Low risk | High risk |
| Lebenthal 1981 [40] | High risk | High risk | High risk | High risk | High risk | High risk | High risk |
| Maagard 2016 [36] | High risk | Unclear risk | High risk | Unclear | High risk | Low risk | High risk |
| Ong 2010 [30] | Low risk | Unclear risk | Low risk | Unclear | Low risk | Low risk | Low risk |
| Pedersen 2014 [29] | Low risk | Low risk | High risk | High risk | High risk | High risk | High risk |
| Pedersen 2014 [32] | High risk | High risk | High risk | High risk | High risk | Low risk | High risk |
| Staudacher 2011 [21] | Unclear | High risk | High risk | High risk | Unclear | High risk | High risk |
| Staudacher 2012 [27] | Low risk | Low risk | Low risk | High risk | High risk | High risk | Low risk |
| Valeur 2016 [35] | High risk | High risk | High risk | High risk | High risk | Low risk | High risk |
| Wildersmith 2017 [34] | High risk | High risk | High risk | High risk | low risk | Low risk | High risk |
| Wintermeyer 2012 [44] | High risk | High risk | High risk | High risk | High risk | High risk | High risk |