Table 1 Characteristics of articles of parallel group randomized trials by year of publication
| Year of Publication |
2000 (n = 355) |
2006 (n = 421) |
% difference†
(95% CI) | P-value |
|---|---|---|---|---|
| Outcome specification | ||||
| Primary | 180 (50.7%) | 273 (64.9%) | 14.1 (7.2 to 21.0) | <0.0001 |
| Unspecified | 175 (49.3%) | 148 (35.1%) | ||
| Centre involved* | ||||
| Multiple centres | 119 (34.1%) | 138 (33.7%) | -0.4 (-7.2 to 6.3) | 0.9 |
| Single centre | 230 (65.9%) | 272 (66.3%) | ||
| Number of intervention groups | 261 (73.5%) | 328 (77.9%) | 0.2 | |
| 2 | 57 (16.1%) | 64 (15.2%) | ||
| 3 | 37 (10.4%) | 29 (6.9%) | ||
| > 3 | ||||
| Performed stratified randomisation | 56 (15.8%) | 85 (20.2%) | 4.4 (-1.0 to 9.8) | 0.1 |
| Sample size | ||||
| < 50 | 116 (32.7%) | 129 (30.6%) | ||
| 51 - 150 | 141 (39.7%) | 169 (39.9%) | ||
| 151 - 300 | 49 (13.8%) | 52 (12.4%) | ||
| 301 - 450 | 20 (5.6%) | 27 (6.6%) | ||
| > 450 | 29 (8.2%) | 44 (10.5%) | ||
| Median (10th to 90th percentile) | 91 (27 to 394) | 80 (28 to 462) | 0.7 | |
| Journal type | ||||
| General medical | 31 (8.7%) | 36 (8.6%) | -0.1 (3.8 to -4.2) | 0.9 |
| Specialty | 324 (91.3%) | 385 (91.4%) | ||
| Number of outcomes per trial | ||||
| Median (range) | 15 (1, 131) | 14 (1, 372) | 0.2 | |
| Type of outcomes | (n = 7132) | (n = 8299) | <0.0001 | |
| Continuous | 4984 (69.9%) | 5705 (68.7%) | ||
| Binary | 1961 (27.5%) | 2357 (28.4%) | ||
| Time-to-event | 47 (0.6%) | 128 (1.5%) | ||
| Ordinal | 140 (2.0%) | 98 (1.2%) | ||
| Categorical | 0 | 11 (0.1%) | ||
| Adjusted analysis | 84 (23.7%) | 113 (26.8%) | 3.1 (-2.9 to 9.3) | 0.3 |