Reported presence of a data monitoring committee stratified by trial characteristics
| Trial characteristic | N | Data monitoring committee, N (%) | P value | |
| Reported 55 (18) | Not reported 245 (82) | |||
| Number of centres | ||||
| Single centre | 139 | 14 (10) | 125 (90) | <0.001 |
| Multicentre | 132 | 41 (31) | 91 (69) | |
| Unclear | 29 | 0 (0) | 29 (100) | |
| Number of nations | ||||
| Single nation | 281 | 48 (17) | 233 (83) | 0.06 |
| Multinational | 19 | 7 (37) | 12 (63) | |
| Sample size | ||||
| N randomised, median (range) | 300 | 224 (10–60480) | 91 (10–9528) | <0.001 |
| Nature of the intervention | ||||
| Drug | 85 | 27 (32) | 58 (68) | 0.001 |
| Vaccine | 14 | 5 (36) | 9 (64) | |
| Rehabilitation or psychosocial | 30 | 1 (3) | 29 (97) | |
| Prevention or screening | 14 | 3 (21) | 11 (79) | |
| Surgery or radiotherapy | 9 | 0 (0) | 9 (100) | |
| Communication, organisational or educational | 52 | 4 (8) | 48 (92) | |
| Alternative therapeutic | 14 | 4 (29) | 10 (71) | |
| Device | 29 | 2 (7) | 27 (93) | |
| Other* | 53 | 9 (17) | 44 (83) | |
| Primary outcome type | ||||
| Behavioural | 46 | 4 (9) | 42 (91) | 0.16 |
| Biomarker | 55 | 12 (22) | 43 (78) | |
| Pain | 14 | 3 (21) | 11 (79) | |
| Physiological | 130 | 31 (24) | 99 (76) | |
| Psychological | 28 | 2 (7) | 26 (93) | |
| Techniques/training | 13 | 1 (8) | 12 (92) | |
| Quality of life | 5 | 0 (0) | 5 (100) | |
| Other | 9 | 2 (22) | 7 (78) | |
| Industry or pharmaceutical funding | ||||
| Yes | 50 | 16 (32) | 34 (68) | 0.009 |
| No | 250 | 39 (16) | 211 (84) | |
*Included therapeutic nutritional interventions (eg, supplements, infant formula and probiotics), sensorimotor interventions, physical activity interventions and financial interventions.