Table 3 Risk of bias of included non-randomized studies
Author/year of publication | Bias due to confounding | Bias in selection of participants into the study | Bias in classification of interventions | Bias due to deviations from intended interventions | Bias due to missing data | Bias in measurement of outcomes | Bias in selection of the reported result | Overall |
|---|---|---|---|---|---|---|---|---|
Bitra et al. 2017 [21] | Low risk | Low risk | Low risk | Low risk | Low risk | Moderate risk | Low risk | Moderate risk |
Smuthkochorn et al. 2017 [22] | Low risk | Low risk | Low risk | Low risk | Low risk | Moderate risk | Low risk | Moderate risk |
Yang et al. 2014 [23] | Serious risk | Low risk | Low risk | Low risk | Low risk | Moderate risk | Low risk | Serious risk |
Alfaqeeh et al. 2011 [24] | Low risk | Low risk | Low risk | Low risk | Low risk | Moderate risk | Low risk | Moderate risk |
Batra et al. 2006 [25] | Critical risk | Low risk | Low risk | Low risk | Low risk | Moderate risk | Low risk | Critical risk |
Isik et al. 2005 [26] | Critical risk | Low risk | Low risk | Low risk | Low risk | Moderate risk | Low risk | Critical risk |
Perinetti et al. 2004 [27] | Low risk | Low risk | Low risk | Low risk | Low risk | Moderate risk | Low risk | Moderate risk |
Perinetti et al. 2002 [28] | Low risk | Low risk | Low risk | Low risk | Low risk | Moderate risk | Low risk | Moderate risk |
Griffiths et al. 1998 [29] | Serious risk | Low risk | Low risk | Low risk | Low risk | Moderate risk | Low risk | Serious risk |