Table 2. Risk of bias within non-randomized trials using the Newcastle-Ottawa scale.
| Study (yr) | Selection | Comparability | Exposure/outcome | |||||
|---|---|---|---|---|---|---|---|---|
| Is the case definition adequate? | Representativeness of the cases | Selection of controls | Definition of controls | Comparability of cohorts | Ascertainment of exposure | Same methods of ascertainment for cases and controls | Non-response rate | |
| Adrie (2013) | ★ | ★ | ★ | NA | ★ | ★ | ★ | NA |
| Bratzler (2008) | ★ | ★ | ★ | NA | NA | ★ | ★ | NA |
| Karhu (2013) | ★ | ★ | ★ | NA | ★★ | ★ | ★ | NA |
| Martin-Loeches (2010) | ★ | NA | ★ | NA | NA | ★ | ★ | NA |
| Mortensen (2006) | ★ | ★ | ★ | NA | NA | ★ | ★ | NA |
| Waterer (2001) | ★ | ★ | ★ | NA | NA | ★ | ★ | NA |
| Wilson (2012) | ★ | ★ | ★ | NA | ★★ | ★ | ★ | NA |
A maximum of one star for the selection and exposure/outcome domains and two stars for the comparability domain were assigned. Studies with stars in all domains (excluding comparability) were considered high quality.
NA = not applicable.