Table 1. Characteristics of the included studies.
| 1988 (%) | 1998 (%) | 2008 (%) | P Value | |
|---|---|---|---|---|
| STUDY DESIGN | N = 601 | N = 568 | N = 502 | |
| PROSPECTIVE STUDIES | 483 (80%) | 422 (74%) | 370 (74%) | 0.013 |
| Prospective randomized | 131 (22%) | 203 (36%) | 232 (46%) | < 0.0001 |
| Prospective non-randomized | 352 (59%) | 219 (39%) | 138 (27%) | < 0.0001 |
| Prospective randomized single-center | 67 (11%) | 49 (9%) | 25 (5%) | 0.001 |
| Prospective randomized multi-center | 64 (11%) | 154 (27%) | 207 (41%) | < 0.0001 |
| Prospective non-randomized single-center | 282 (47%) | 99 (17%) | 52 (10%) | < 0.0001 |
| Prospective non-randomized multi-center | 70 (12%) | 120 (21%) | 86 (17%) | < 0.0001 |
| RETROSPECTIVE STUDIES | 118 (20%) | 146 (26%) | 132 (26%) | 0.013 |
| Registry | 52 (9%) | 51 (9%) | 73 (14%) | 0.002 |
| Meta-analysis | 13 (2%) | 8 (2%) | 18 (4%) | 0.059 |
| Other * | 53 (9%) | 87 (15%) | 41 (8%) | 0.0001 |
| Study Size (median number of patients) | 103 | 595 | 1380 | 0.20 |
| FUNDING | ||||
| Reported funding | 388 (65%) | 471 (83%) | 469 (93%) | |
| Government | 288 (74%) | 339 (72%) | 326 (70%) | 0.31 |
| Industry | 65 (17%) | 130 (28%) | 186 (40%) | < 0.0001 |
| Non-profit | 167 (43%) | 177 (38%) | 188 (40%) | 0.27 |
| No funding / None reported | 213 (35%) | 97 (17%) | 33 (7%) | < 0.0001 |
| Single funding | 234 (39%) | 199 (35%) | 172 (34%) | 0.22 |
| Multiple funding | 154 (26%) | 272 (48%) | 297 (59%) | < 0.0001 |
| Disclosure of positive COI | 10 (2%) | 34 (6%) | 280 (56%) | < 0.0001 |
| Disclosure of negative COI | 0 (0%) | 4 (1%) | 141 (28%) | <0.0001 |
| No disclosure provided | 591 (98%) | 530 (93%) | 81 (16%) | <0.0001 |
| OUTCOMES | ||||
| Positive | 543 (90%) | 477 (84%) | 394 (78%) | < 0.0001 |
| Negative | 58 (10%) | 91 (16%) | 108 (22%) | < 0.0001 |
* case control studies, cross-sectional studies, case reports