Association between characteristics of the search and inclusion criteria of primary studies and assessment of publication bias
| Variable | Total (n = 225) | Assessment of publication bias n (%) | RR (95% CI) |
|---|---|---|---|
| Use of Medline | |||
| Yes | 164 | 22 (13.4) | 2.73 (0.85 to 8.79) |
| No | 61 | 3 (4.9) | 1 (ref) |
| Use of Embase | |||
| Yes | 64 | 8 (12.5) | 1.18 (0.54 to 2.61) |
| No | 161 | 17 (10.6) | 1 (ref ) |
| Use of other databases | |||
| Yes | 114 | 18 (15.8) | 2.50 (1.09 to 5.76) |
| No | 111 | 7 (6.3) | 1 (ref) |
| Use of several databases | |||
| ⩾4 | 35 | 7 (20.0) | 2.48 (1.07 to 5.75) |
| 3 | 29 | 5 (17.2) | 2.14 (0.82 to 5.54) |
| 2 | 161 | 13 (8.1) | 1 (ref) |
| Handsearch in references of articles | |||
| Yes | 131 | 19 (14.5) | 2.27 (0.94 to 5.47) |
| No | 94 | 6 (6.4) | 1 (ref) |
| Search using other languages than English | |||
| Yes | 50 | 7 (14.0) | 1.36 (0.60 to 3.07) |
| No | 175 | 18 (10.3) | 1 (ref) |
| Search of non-published reports | |||
| Yes | 58 | 5 (8.6) | 0.72 (0.28 to 1.83) |
| No | 167 | 20 (12.0) | 1 (ref) |
| Consultation with researchers to identify non-published studies | |||
| Yes | 40 | 1 (2.5) | 0.19 (0.03 to 1.38) |
| No | 185 | 24 (13.0) | 1 (ref) |
| Search in Scientific Meetings | |||
| Yes | 26 | 4 (15.4) | 1.46 (0.54 to 3.92) |
| No | 199 | 21 (10.6) | 1 (ref) |
| Study quality in the inclusion criteria | |||
| Yes | 36 | 3 (8.3) | 0.72 (0.23 to 2.27) |
| No | 189 | 22 (11.6) | 1(ref) |