Table 4. Association Between Trial Registration Status and Journal and Trial Characteristics for the 953 Trials.
| Variable | Trial Registration Status, No. (%) | Total, No. (N = 953) | |||||
|---|---|---|---|---|---|---|---|
| Prospective Registration (N = 189) | Registration During Trial (N = 141) | Registration After Trial (N = 120) | Late Registration [timing unclear] (N = 4)a | No Registration (N = 496) | Pre-ICMJE Policy (N = 3) | ||
| Journal Characteristics | |||||||
| Journal registration policy that applied to the trial | |||||||
| Prospective registration required | 33 (33.7) | 19 (19.4) | 15 (15.3) | 0 | 31 (31.6) | 0 | 98 |
| Registration required without timing | 40 (24.5) | 30 (18.4) | 44 (27.0) | 0 | 48 (29.4) | 1 (0.6) | 163 |
| No registration required | 116 (16.9) | 92 (13.4) | 61 (8.9) | 4 (0.6) | 410 (59.9) | 2 (0.3) | 685 |
| Undeterminedb | 0 | 0 | 0 | 0 | 7 (100) | 0 | 7 |
| Impact factor and registration policy by impact factorc | |||||||
| 0.0-1.9 | 35 (9.8) | 38 (10.6) | 41 (11.5) | 1 (0.3) | 243 (67.9) | 0 | 358 |
| Prospective registration required | 8 (17.8) | 7 (15.6) | 9 (20.0) | 0 | 21 (46.7) | 0 | 45 |
| Prospective registration not requiredd | 27 (8.7) | 31 (9.9) | 32 (10.3) | 1 (0.3) | 221 (70.8) | 0 | 312 |
| Undeterminedb | 0 | 0 | 0 | 0 | 1 (100) | 0 | 1 |
| 2.0-3.9 | 95 (20.4) | 72 (15.5) | 60 (12.9) | 2 (0.4) | 235 (50.4) | 2 (0.4) | 466 |
| Prospective registration required | 11 (42.3) | 6 (23.1) | 3 (11.5) | 0 | 6 (23.1) | 0 | 26 |
| Prospective registration not requiredd | 84 (19.4) | 66 (15.2) | 57 (13.1) | 2 (0.5) | 223 (51.4) | 2 (0.5) | 434 |
| Undeterminedb | 0 | 0 | 0 | 0 | 6 (100) | 0 | 6 |
| ≥4.0 | 59 (45.7) | 31 (24.0) | 19 (14.7) | 1 (0.8) | 18 (14.0) | 1 (0.8) | 129 |
| Prospective registration required | 14 (51.9) | 6 (22.2) | 3 (11.1) | 0 | 4 (14.8) | 0 | 27 |
| Prospective registration not requiredd | 45 (44.1) | 25 (24.5) | 16 (15.7) | 1 (1) | 14 (13.7) | 1 (1) | 102 |
| Undeterminedb | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Publisher | |||||||
| Elsevier | 39 (21.2) | 26 (14.1) | 25 (13.6) | 0 | 94 (51.1) | 0 | 184 |
| Wiley | 31 (25.0) | 20 (16.1) | 13 (10.5) | 2 (1.6) | 58 (46.8) | 0 | 124 |
| Wolters Kluwer | 19 (20.2) | 14 (14.9) | 9 (9.6) | 0 | 50 (53.2) | 2 (2.1) | 94 |
| Springer | 15 (19.7) | 12 (15.8) | 6 (7.9) | 0 | 43 (56.6) | 0 | 76 |
| Sage | 18 (25.7) | 12 (17.1) | 10 (14.3) | 0 | 29 (41.4) | 1 (1.4) | 70 |
| Taylor & Francis | 10 (19.2) | 8 (15.4) | 7 (13.5) | 0 | 27 (51.9) | 0 | 52 |
| IPEC Press | 0 | 0 | 0 | 0 | 44 (100) | 0 | 44 |
| Biomed Central | 8 (23.5) | 4 (11.8) | 15 (44.1) | 0 | 7 (20.6) | 0 | 34 |
| Cambridge University Press | 7 (21.2) | 6 (18.2) | 2 (6.1) | 1 (3.0) | 17 (51.5) | 0 | 33 |
| NRC Research Press | 3 (10.0) | 2 (6.7) | 3 (10.0) | 0 | 22 (73.3) | 0 | 30 |
| American Society for Nutrition | 12 (42.9) | 8 (28.6) | 7 (25.0) | 0 | 1 (3.6) | 0 | 28 |
| MDPI open access | 4 (17.4) | 4 (17.4) | 6 (26.1) | 0 | 9 (39.1) | 0 | 23 |
| Human Kinetics | 0 | 2 (10.5) | 1 (5.3) | 0 | 16 (84.2) | 0 | 19 |
| American Psychological Association | 1 (6.2) | 2 (12.5) | 0 | 0 | 13 (81.2) | 0 | 16 |
| IOS Press | 0 | 1 (6.2) | 1 (6.3) | 0 | 14 (87.5) | 0 | 16 |
| Karger | 5 (45.5) | 2 (18.2) | 3 (27.3) | 0 | 1 (9.1) | 0 | 11 |
| Other | 17 (17.2) | 18 (18.2) | 12 (12.1) | 1 (1.0) | 51 (51.5) | 0 | 99 |
| Trial Characteristics | |||||||
| Category of nonregulated intervention based on journal where publishede | |||||||
| Behavioral sciences or psychology | 35 (27.3) | 16 (12.5) | 15 (11.7) | 1 (0.8) | 61 (47.7) | 0 | 128 |
| Nursing | 7 (5.7) | 17 (13.9) | 12 (9.8) | 0 | 86 (70.5) | 0 | 122 |
| Nutrition and dietetics | 62 (23.5) | 36 (13.6) | 49 (18.6) | 2 (0.8) | 114 (43.2) | 1 (0.4) | 264 |
| Rehabilitation | 49 (17.8) | 42 (15.3) | 30 (10.9) | 1 (0.4) | 152 (55.3) | 1 (0.4) | 275 |
| Surgery | 39 (21.4) | 30 (16.5) | 16 (8.8) | 0 | 96 (52.7) | 1 (0.5) | 182 |
| Corresponding author country | |||||||
| Australia | 22 (44.0) | 9 (18.0) | 4 (8.0) | 1 (2.0) | 14 (28.0) | 0 | 50 |
| Brazil | 11 (24.4) | 8 (17.8) | 10 (22.2) | 0 | 16 (35.6) | 0 | 45 |
| Canada | 9 (21.4) | 3 (7.1) | 7 (16.7) | 0 | 23 (54.8) | 0 | 42 |
| China | 5 (10.4) | 4 (8.3) | 5 (10.4) | 0 | 34 (70.8) | 0 | 48 |
| Denmark | 7 (46.7) | 6 (40.0) | 1 (6.7) | 0 | 1 (6.7) | 0 | 15 |
| Egypt | 0 | 0 | 3 (23.1) | 0 | 10 (76.9) | 0 | 13 |
| Germany | 12 (35.3) | 1 (2.9) | 6 (17.6) | 1 (2.9) | 14 (41.2) | 0 | 34 |
| Greece | 1 (10.0) | 1 (10.0) | 2 (20.0) | 0 | 6 (60.0) | 0 | 10 |
| Iran | 2 (7.7) | 6 (23.1) | 10 (38.5) | 0 | 8 (30.8) | 0 | 26 |
| Italy | 2 (8.0) | 2 (8.0) | 6 (24.0) | 0 | 15 (60.0) | 0 | 25 |
| Japan | 8 (30.8) | 5 (19.2) | 3 (11.5) | 0 | 9 (34.6) | 1 (3.8) | 26 |
| Netherlands | 12 (42.9) | 9 (32.1) | 3 (10.7) | 0 | 4 (14.3) | 0 | 28 |
| New Zealand | 5 (41.7) | 2 (16.7) | 0 | 0 | 5 (41.7) | 0 | 12 |
| Norway | 1 (10.0) | 5 (50.0) | 3 (30.0) | 0 | 1 (10.0) | 0 | 10 |
| South Korea | 6 (8.7) | 0 | 2 (2.9) | 0 | 61 (88.4) | 0 | 69 |
| Spain | 4 (11.8) | 6 (17.6) | 10 (29.4) | 0 | 14 (41.2) | 0 | 34 |
| Sweden | 0 | 8 (50.0) | 3 (18.8) | 0 | 5 (31.3) | 0 | 16 |
| Taiwan | 1 (5.6) | 2 (11.1) | 0 | 0 | 15 (83.3) | 0 | 18 |
| Turkey | 1 (2.3) | 2 (4.7) | 3 (7.0) | 0 | 37 (86.0) | 0 | 43 |
| United Kingdom | 16 (23.5) | 16 (23.9) | 8 (11.8) | 2 (3.0) | 26 (38.2) | 0 | 68 |
| United States | 48 (21.3) | 36 (16.0) | 15 (6.7) | 0 | 125 (55.6) | 1 (0.4) | 225 |
| Other | 16 (16.7) | 10 (10.4) | 16 (16.6) | 0 | 53 (55.2) | 1 (1.0) | 96 |
| Funding | |||||||
| National/state/provincial | 88 (30.3) | 58 (20.0) | 32 (11.0) | 3 (1.0) | 107 (36.9) | 2 (0.7) | 290 |
| Other not-for-profit | 34 (24.2) | 35 (24.8) | 13 (9.2) | 0 | 59 (41.8) | 0 | 141 |
| Industry | 36 (19.0) | 38 (20.1) | 24 (12.7) | 2 (1.1) | 89 (47.1) | 0 | 189 |
| Internal university or hospital | 21 (20.4) | 21 (20.4) | 21 (20.4) | 1 (1.0) | 38 (36.9) | 1 (1.0) | 103 |
| No funding | 20 (17.5) | 7 (6.1) | 24 (21.1) | 1 (0.9) | 62 (54.4) | 0 | 114 |
| Not reported | 27 (10.0) | 23 (8.6) | 25 (9.3) | 0 | 194 (72.1) | 0 | 269 |
| Sample size | |||||||
| 0-49 | 61 (14.6) | 51 (12.2) | 49 (11.8) | 0 | 256 (61.4) | 0 | 417 |
| 50-99 | 55 (22.0) | 41 (16.4) | 31 (12.4) | 2 (0.8) | 121 (48.4) | 0 | 250 |
| ≥100 | 73 (25.6) | 49 (17.2) | 40 (14.0) | 2 (0.7) | 119 (41.6) | 3 (1.1) | 286 |
a
Trials were registered after start of participant enrollment, but it could not be determined if registered prior to collection of trial outcomes or after trial.
b
Undetermined applied when the journal had a conditional registration policy, but dates were not provided to determine the policy that applied to the trial. For analysis of registration policy stratified by impact factor, the 7 undetermined trials were classified as not requiring registration.
c
The percentage of prospectively registered trials was approximately twice as high for journals with a prospective registration policy, compared with journals without a policy (impact factor, <2.0 [P = .10] vs 2.0-3.9 [P < .01]), but was similar across policy status for journals with an impact factor of ≥4 (P = .48). Journal impact factor was correlated with the number of trials published in the 6-mo study period (r = 0.26).
d
This category included journals with a required registration policy that did not include a prospective registration policy and journals with no registration policy.
e
Eighteen trials were published in 4 journals that were listed in more than 1 category of nonregulated interventions.