Supplemental Digital Content Table S1: Subspecialties of RCTs
S1a: Subspecialties of surgical RCTs (n=127)
Numbers (column percentages) are displayed.
Subspecialty Frequency (%) total anesthesiology cardiothoracic dentistry
127 (100)
17 ( 13)
16 ( 13)
2 ( 2) ear-nose-throat (ENT) 6 ( 5) general surgery 8 ( 6) maxillofacial surgery 2 ( 2) neurosurgery 6 ( 5) obstetrics / gynecology 20 ( 16) ophthalmology 18 ( 14) orthopedics plastic surgery transplantation
13 ( 10)
1 ( 1)
3 ( 2) traumatology urology vascular surgery
3 ( 2)
8 ( 6)
4 ( 3)

S1b: Subspecialties of medical RCTs (n=736)
Numbers (column percentages) are displayed.
Subspecialty Frequency (%) total 736 (100) alternative medicine cardiovascular
1 ( <1)
111 ( 15) dermatology 22 ( 3) emergency medicine 2 ( <1) endocrinology gastroenterology
57 ( 8)
48 ( 6) haematology immunology infectious diseases intensive care nephrology neurology oncology physiotherapy psychiatry psychotherapy radiology rehabilitation pneumology rheumatology sports medicine
35 ( 5)
6 ( 1)
80 ( 11)
13 ( 2)
15 ( 2)
58 ( 8)
155 ( 21)
1 ( <1)
41 ( 5)
3 ( <1)
7 ( 1)
6 ( 1)
44 ( 6)
30 ( 4)
1 ( <1)

Supplemental Digital Content Table S2: Multivariable regression for trial discontinuation for slow recruitment of surgical trials disregarding clustering by the approving research ethics committee (n=89 1 ) and after multiple imputation of missing predictor and outcome variables (n=115 2 )
Potential predictor
Industry sponsor, yes versus no
Multivariable, disregarding clustering by research ethics committee
Odds ratio 95% CI 3 P value
Multivariable, multiple imputations
Odds ratio 95% CI P value
0.53 0.19, 1.51 0.235 0.64 0.23, 1.81 0.402
Primary harm outcome, yes versus no 0.55 0.16, 1.91 0.348 0.50 0.14, 1.80 0.291
1 Out of 115 trials, 12 had an unclear completion status and 14 had at least one missing covariate.
2 Exclusion of 10 trials that never started and of 2 that were still recruiting
3 CI=Confidence interval

Supplemental Digital Content Table S3: Multivariable regression for non-publication as full journal article of surgical trials disregarding clustering by the approving research ethics committee (n=89 1 ) and after multiple imputation of missing predictor and outcome variables (n=115 2 )
Potential predictor
Industry sponsor, yes versus no
Multivariable, disregarding clustering by research ethics committee
Odds ratio 95% CI 3 P value
Multivariable, multiple imputations
Odds ratio 95% CI P value
2.99 1.05, 8.58 0.041 1.92 0.81, 4.53 0.137
Primary harm outcome, yes versus no 0.28 0.09, 0.92 0.035 0.30 0.10, 0.90 0.031
1.45, 12.05 0.008 3.32 1.33, 8.33 0.010 Trial discontinuation for any reason, yes versus no
4.18
1 Out of 115 trials, 26 had at least one missing covariate.
2 Exclusion of 10 trials that never started and of 2 that were still recruiting
3 CI=Confidence interval

Supplemental Digital Content Figure S1
Flow chart of included studies, eligibility, descriptive results and risk differences (95% confidence intervals) comparing invasive to noninvasive trials