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General study characteristics (N=83).
| Variables | Studies, n (%) | ||
| Registration of studies and publication of study protocols | |||
| Trials with study registration | 58 (70) | ||
| With study protocol | 21 (25) | ||
| Without study protocol | 37 (45) | ||
| Trials without study registration | 25 (29) | ||
| With study protocol | 1 (1) | ||
| Without study protocol | 24 (28) | ||
| Number of study arms in included trials | |||
| 2 | 64 (77) | ||
| 3 | 16 (19) | ||
| ≥4 | 3 (4) | ||
