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Risk of bias in included studies
| Vallejo 1981 | Veterans 2000 | Edinburgh 2003 | Stassano 2009 | |
|---|---|---|---|---|
| Random sequence generation | Unclear | Unclear | Unclear | Unclear |
| Allocation concealment | Low risk of bias | Low risk of bias | Low risk of bias | Low risk of bias |
| Blinding of outcome assessors | Low risk of bias | Low risk of bias | Low risk of bias | Low risk of bias |
| Complete outcome data | Low risk of bias | Low risk of bias | Low risk of bias | Low risk of bias |
