Table 3. Assessment of methodological quality (Cochrane risk of bias for RCTs, Newcastle-Ottawa for NRSIs).
| RCT [ref] | Sequence generation | Allocation concealment | Blinding of participants and personnel | Blinding of outcome assessors | Incomplete outcome data | Selective outcome reporting | Other |
| Green 2005 4 | Low | Unclear | High | Unclear | Low | Unclear | Low |
| Laine 2010 29 | Low | Low | High | High | Low | Low | High |
| NRSI [ref] | Representativeness (1) | Selection of non-exposed (1) | Ascertainment of exposure (1) | Outcome of interest not present at start of study (1) | Comparability (2) | Assessment of outcome (1) | Follow-up long enough and adequate (2) |
| Adeldawi 2014 24 | 1 | 1 | 1 | 1 | 1/0 | 1 | 1/1 |
| Ishii 2011 17 | 0 | 1 | 1 | 1 | 0/0 | 1 | 1/1 |
| Jacovides 2015 25 | 1 | 1 | 1 | 0 | 0/1 | 1 | 1/1 |
| Jensen 2000 30 | 0 | 1 | 1 | 1 | 0/0 | 1 | 1/1 |
| Nagata 2016 27 | 1 | 1 | 1 | 1 | 1/1 | 1 | 1/1 |
| Nagata 2015 26 | 1 | 1 | 1 | 1 | 1/0 | 1 | 1/1 |
| Nakano 2015 22 | 0 | 1 | 1 | 1 | 0/0 | 1 | 1/0 |
| Sun 2011 20 | 0 | 0 | 1 | 1 | 0/0 | 1 | 1/1 |
| Yabutani 2014 21 | 0 | 1 | 1 | 0 | 1/1 | 1 | 1/1 |
| Yamaguchi 2006 23 | 1 | 1 | 1 | 1 | 1/1 | 1 | 1/1 |
| Ketwaroo 2012 18 | 0 | 0 | 1 | 1 | 0/0 | 1 | 1/1 |
| Strate 2003 28 | 1 | 1 | 1 | 1 | 1/1 | 1 | 1/1 |
| Rodriguez-Moranta 2007 19 | 1 | 1 | 1 | 1 | 1/1 | 1 | 1/1 |