Table 2.
Methodological items of included studies
| Items | Overall (n=1122) (No, col %) | Not registered (n=529) (No, row %) | Registered (n=593) (No, row %) | P value | Prospectively registered (n=220) (No, row %)* | Retrospectively r (n=373) (No, row %)* | P value† |
|---|---|---|---|---|---|---|---|
| Defined primary outcome reported: | |||||||
| Yes | 779 (69.4) | 256 (32.9) | 523 (67.1) | <0.001 | 200 (25.7) | 323 (41.5) | <0.001 |
| No | 343 (30.6) | 273 (79.6) | 70 (20.4) | 20 (5.8) | 50 (14.6) | ||
| Sample size calculation reported: | |||||||
| Yes | 622 (55.4) | 195 (31.4) | 427 (68.6) | <0.001 | 159 (25.6) | 268 (43.1) | <0.001 |
| No | 500 (44.6) | 334 (66.8) | 166 (33.2) | 61 (12.2) | 105 (21.0) | ||
| Random sequence generation: | |||||||
| Computer | 456 (40.6) | 169 (37.1) | 287 (62.9) | <0.001 | 109 (23.9) | 178 (39.0) | <0.001 |
| Random number table | 69 (6.2) | 44 (63.8) | 25 (36.2) | 3 (4.4) | 22 (31.9) | ||
| Not reported or inadequate | 555 (49.5) | 288 (51.9) | 267 (48.1) | 103 (18.6) | 162 (29.6) | ||
| Other | 42 (3.7) | 28 (66.7) | 14 (33.3) | 5 (11.9) | 9 (21.4) | ||
| Allocation concealment: | |||||||
| Envelope | 209 (18.6) | 91 (43.5) | 118 (56.5) | <0.001 | 24 (11.5) | 94 (45.0) | <0.001 |
| Central | 100 (8.9) | 12 (12.0) | 88 (88.0) | 48 (48.0) | 40 (40.0) | ||
| Pharmacy | 44 (3.9) | 9 (20.5) | 35 (79.5) | 18 (40.9) | 17 (38.6) | ||
| Not reported or inadequate | 731 (65.2) | 402 (55.0) | 329 (45.0) | 125 (17.1) | 204 (27.9) | ||
| Other | 38 (3.4) | 15 (39.5) | 23 (60.5) | 5 (13.2) | 18 (47.4) | ||
| Blinding, how?: | |||||||
| Blinded, details given | 265 (23.6) | 94 (35.5) | 171 (64.5) | <0.001 | 73 (27.6) | 98 (37.0) | <0.001 |
| Blinded, no details given | 416 (37.1) | 172 (41.5) | 244 (58.7) | 97 (23.3) | 147 (35.3) | ||
| Unblinded | 181 (16.1) | 94 (51.9) | 87 (48.1) | 20 (11.1) | 67 (37.0) | ||
| Not reported | 260 (23.2) | 169 (65.0) | 91 (35.0) | 30 (11.5) | 61 (23.5) | ||
| Blinding, who?: | |||||||
| Reported, details given | 507 (45.2) | 210 (41.4) | 297 (58.6) | <0.001 | 115 (22.7) | 182 (35.9) | <0.001 |
| Reported, no details given | 170 (15.2) | 52 (30.6) | 118 (69.4) | 55 (32.4) | 63 (37.1) | ||
| Unblinded | 181 (16.1) | 94 (51.9) | 87 (48.1) | 20 (11.1) | 67 (37.0) | ||
| Unclear | 264 (23.5) | 173 (65.5) | 91 (34.5) | 30 (11.4) | 61 (23.1) | ||
| Attrition: | |||||||
| Yes, details given | 625 (55.7) | 202 (32.3) | 423 (67.7) | <0.001 | 168 (26.9) | 255 (40.8) | <0.001 |
| Yes, details not given | 120 (10.7) | 57 (47.5) | 63 (52.5) | 18 (15.0) | 45 (37.5) | ||
| No | 377 (33.6) | 270 (71.6) | 107 (28.4) | 34 (9.0) | 73 (19.4) | ||
| Intention to treat: | |||||||
| Intention to treat | 312 (27.8) | 74 (23.7) | 238 (76.3) | <0.001 | 87 (27.9) | 151 (48.4) | <0.001 |
| No intention to treat | 810 (72.2) | 455 (56.2) | 355 (43.8) | 133 (16.4) | 222 (27.4) |
*
Percentages from 3×2 table including trials prospectively registered, retrospectively registered, and not registered.
†
Generated from χ2 test comparing proportion of trials prospectively registered, retrospectively registered, and not registered.