Table 2.
Summary of risk of bias assessment in included studies. Values are numbers (percentages) unless stated otherwise
| Assessment item | Risk level | No of studies assessed | ||
|---|---|---|---|---|
| Low | Unclear | High | ||
| Random sequence generation (selection bias) | 85 (49) | 80 (46) | 10 (6) | 175 |
| Allocation concealment (selection bias) | 49 (28) | 116 (66) | 10 (6) | 175 |
| Blinding of participants and staff (performance bias) | 8 (5) | 123 (73) | 37 (22) | 168 |
| Blinding of outcome assessment (detection bias): all outcomes | 20 (15) | 107 (81) | 5 (4) | 132 |
| Blinding of outcome assessment (detection bias): patient reported outcomes | 4 (11) | 17 (47) | 15 (42) | 36 |
| Blinding of outcome assessment (detection bias): clinician measured outcomes | 8 (22) | 20 (56) | 8 (22) | 36 |
| Blinding (performance bias and detection bias) | 1 (14) | 6 (86) | 0 (0) | 7 |
| Incomplete outcome data (attrition bias): all outcomes | 54 (39) | 76 (55) | 9 (6) | 139 |
| Incomplete outcome data (attrition bias): patient: reported outcomes | 18 (50) | 16 (44) | 2 (6) | 36 |
| Incomplete outcome data (attrition bias): clinician measured outcomes | 21 (58) | 13 (36) | 2 (6) | 36 |
| Selective reporting (reporting bias) | 24 (65) | 7 (19) | 6 (16) | 37 |
| Other bias | 0 (0) | 82 (100) | 0 (0) | 82 |
Reflecting different publication dates of Cochrane reviews, different versions of Cochrane risk of bias tool were used. Risk of bias domains assessed were not consistent across Cochrane reviews included in this evidence synthesis.