Table 1.
Characteristics of included trials
| Trial characteristics | All trials (n=405) |
Concluded (n=313) |
Potentially ongoing (n=92) |
| Number of participants, median (IQR) | 80 (32–225) | 80 (30–230) | 80 (40–173) |
| Trial phase, n (%) | |||
| Phase 2 | 186 | 147 (79) | 39 (21) |
| Phase 3 or 2/3 | 132 | 101 (77) | 31 (23) |
| Phase 4 | 87 | 65 (75) | 22 (25) |
| Funding source, n (%)* | |||
| Industry | 214 | 187 (87) | 27 (13) |
| NIH/US government | 23 | 17 (74) | 6 (26) |
| Other | 233 | 155 (67) | 78 (33) |
| Trial start date, n (%) | |||
| Unlisted | 2 | 1 (50) | 1 (50) |
| Prior to 2006 | 15 | 14 (93) | 1 (7) |
| 2006–2009 | 37 | 29 (78) | 8 (22) |
| 2010–2011 | 235 | 176 (75) | 59 (25) |
| 2012–2014 | 116 | 93 (80) | 23 (20) |
| Registered retrospectively, n (%)† | 159 | 124 (78) | 35 (22) |
| Registered prospectively, n (%) | 245 | 189 (77) | 56 (23) |
| Major discrepancy in recruitment status‡ | 125 | 91 (73) | 34 (27) |
*Trials could have more than one funding source.
†Registration timing relative to recruitment could not be determined for one study.
‡Listed recruitment status within ClinicalTrials.gov was incorrect or there was a delay of more than 1 year between when the study concluded and when the registry recruitment status was updated to reflect that recruitment ended.
NIH, National Institutes of Health.