Table 1 Characteristics of large randomized trials registered with ClinicalTrials.gov prior to 2009. Values are numbers (percentages) unless stated otherwise
| Trial characteristics | All trials (n=585) | Published trials (n=414) | Unpublished trials (n=171) |
|---|---|---|---|
| Mean (SD) No of participants | 1693 (5580) | 1668 (3217) | 1753 (9045) |
| Trial phase*: | |||
| I/II | 84 (14) | 43 (10) | 41 (24) |
| III | 394 (67) | 290 (70) | 104 (61) |
| IV | 58 (10) | 40 (10) | 18 (11) |
| Other | 49 (8) | 41 (10) | 8 (5) |
| Funding source†: | |||
| Industry | 468 (80) | 318 (77) | 150 (88) |
| NIH/US government | 64 (11) | 53 (13) | 11 (6) |
| Other | 104 (18) | 84 (20) | 20 (12) |
| Trial completion date: | |||
| Unlisted | 43 (7) | 25 (6) | 18 (11) |
| Prior to 2005 | 11 (2) | 8 (2) | 3 (2) |
| 2005-06 | 93 (16) | 71 (17) | 22 (13) |
| 2007 | 192 (33) | 137 (33) | 55 (32) |
| 2008 | 246 (42) | 173 (42) | 73 (43) |
NIH=National Institutes of Health.
*Trials described as “phase II/III” in their registry entry are categorized as phase III.
†Trials with multiple funding sources are listed within all relevant categories; totals therefore add to more than 100%.