Table 1.
Transparency of aims in formula trials published between 2015 and 2020
| Trials | Total | |||
|---|---|---|---|---|
| Prospectively registered | Non-prospectively registered | Unregistered | ||
| Issues with definition of study aim: | ||||
| Unclear which arm is control group, or whether aim is superiority, equivalence, or non-inferiority | 12/57 (21) | 6/35 (17) | 8/33 (24) | 26/125 (21) |
| Dataset inappropriate for stated aim of trial | 9/57 (16) | 6/35 (17) | 5/33 (15) | 20/125 (16) |
| Clear study aim | 36/57 (63) | 23/35 (66) | 20/33 (61) | 79/125 (63) |
| Issues with description of primary outcome: | ||||
| Multiple primary outcomes or unclear description of primary outcome | 12/57 (21) | 7/35 (20) | 16/33 (48) | 35/125 (28) |
| Timing or measurement method for evaluating primary outcome unclear | 11/57 (19) | 13/35 (37) | 7/33 (21) | 31/125 (25) |
| Clear primary outcome | 34/57 (60) | 15/35 (43) | 10/33 (30) | 59/125 (47) |
| Both study aim and primary outcome clearly described | 26/57 (46) | 10/35 (29) | 7/33 (21) | 43/125 (34) |
| Protocol availability: | ||||
| Prospective protocol publicly available, or provided by author or funder on request | 9/57 (16) | 2/35 (6) | 0/33 (0) | 11/125 (9) |
| Retrospective or undated protocol publicly available, or provided by author or funder on request | 10/57 (18) | 9/35 (26) | 0/33 (0) | 19/125 (15) |
| Author or funder declined to provide protocol | 20/57 (35) | 5/35 (14) | 2/33 (6) | 27/125 (22) |
| Author or funder responded but did not provide protocol | 5/57 (9) | 8/35 (23) | 6/33 (18) | 19/125 (15) |
| No response from author or funder and no publicly available protocol | 13/57 (23) | 11/35 (31) | 25/33 (76) | 49/125 (39) |
| Prospective protocol and clear study aim and clear primary outcome | 8/57 (14) | 0/35 (0) | 0/35 (0) | 8/125 (6) |
Values are No of trials/total No of trials (%).
Prospective trial registration was defined as trial registration in a clinical trial registry approved by the World Health Organization before, or up to one month after, the reported start of the study. Corresponding authors were contacted to request trial protocols and statistical analysis plans up to three times. Only four statistical analysis plans were received: one undated, three dated, two to 13 months after completion of the study.