Table 4.
Risk of Bias Assessments and Study Quality.
| Study | Study Design/Risk of Bias Scale | Main Source of Risk of Bias | Qualitya within study design category | Qualitya across study designs |
|---|---|---|---|---|
| Manning 2002(32) | Randomized Controlled Trial/Cochrane Risk of Bias Tool | Incomplete Outcome Data, selective outcome reporting, significant baseline imbalance | Low | Moderate |
| Machado 2008(30) | Randomized Controlled Trial/Cochrane Risk of Bias Tool | Low risk of bias | High | High |
| Yilmaz 2011(31) | Randomized Controlled Trial/Cochrane Risk of Bias Tool | No description of randomization, allocation concealment or blinding | Moderate | High |
| Szekac 2000(24) | Observational Study/Newcastle-Ottawa Scale, Cohort study | Low risk of bias | High | Moderate |
| Monster 2000(9) | Observational Study/Newcastle-Ottawa Scale, Case-Control study | Low risk of bias | High | Moderate |
| Fencki 2003(23) | Observational Study/Newcastle-Ottawa Scale, Cohort study | Low risk of bias | High | Moderate |
| Agarwal 2005(11) | Observational Study/Newcastle-Ottawa Scale, Cohort study | Low risk of bias | High | Moderate |
| Schopick 2009(12) | Observational Study/Newcastle-Ottawa Scale, Cohort study | Ensuring outcome was not present at beginning | Moderate | Low |
| Fung 2011(10) | Observational Study/Newcastle-Ottawa Scale, Cohort study | Low risk of bias | High | Moderate |
| Kaygusz 2012(41) | Observational Study/Newcastle-Ottawa Scale, Cohort study | Minimal description of cohort, did not ensure outcome was not present at beginning | Low | Very low |
| Vitolo 2015(42) | Observational Study/Newcastle-Ottawa Scale, Cohort study | Minimal description of cohort and exposure | Low | Very low |
| Manning 2002(32) | Observational Study/Newcastle-Ottawa Scale, Cohort study | Ensuring outcome was not present at beginning | Moderate | Low |
a
Each study was given a very low, low, moderate or high quality designation based on the risk of bias (Newcastle-Ottawa Scale for observational studies and Cochrane Risk of Bias Assessment for Randomized Controlled Trials) and the hierarchy of study methodology