Table 1

Main study characteristics: operational, dissemination and design information

InterventionalObservationalOverall
Number of studies43084514
Operational
Status
 Ongoing134 (31%)28 (33%)162 (32%)
 Closed227 (53%)49 (58%)276 (54%)
 Not yet recruiting21 (5%)2 (2%)23 (5%)
 Withdrawn11 (3%)1 (1%)12 (2%)
 Unknown status37 (9%)4 (5%)41 (8%)
Sponsor
 Academic339 (79%)69 (82%)408 (79%)
 Industry91 (21%)15 (18%)106 (21%)
Location
 North America248 (58%)44 (53%)292 (57%)
 Europe97 (23%)29 (35%)126 (25%)
 Asia46 (11%)6 (7%)52 (10%)
 Intercontinental20 (5%)4 (5%)24 (5%)
 Other14 (3%)1 (1%)15 (3%)
 Unknown5 (1%)5 (1%)
Number of centres
 Monocentric257 (60%)49 (58%)306 (60%)
 Multicentric national119 (28%)21 (25%)140 (27%)
 Multicentric international24 (6%)9 (11%)33 (6%)
 Unknown30 (7%)5 (6%)35 (7%)
Dissemination
Published results among closed studies* (n=276)
 Has results on clinicaltrials.gov49 (22%)2 (4%)51 (18%)
 Publication on PubMed40 (18%)5 (10%)45 (16%)
Design
Blinded
 No286 (67%)286 (56%)
 Yes144 (33%)144 (28%)
 Not applicable84 (100%)84 (16%)
Study arms
 Single arm136 (32%)67 (80%)203 (39%)
 Multiarm294 (68%)17 (20%)311 (61%)
Randomisation
 No152 (35%)152 (30%)
 Yes278 (65%)278 (54%)
 Not applicable84 (100%)84 (16%)
Number of primary outcomes
 1337 (78%)65 (77%)402 (78%)
 238 (9%)5 (6%)43 (8%)
 ≥342 (10%)8 (10%)50 (10%)
 Unknown13 (3%)6 (7%)19 (4%)
Actual sample size among closed studies (n=276)
 Median607460
 IQR21–15038–25523–177
 Number of studies22149270
Planned sample size among non-closed studies (n=238)
 Median7223080
 IQR30–17650–50038–200
 Number of studies20235237
  • *On clinicaltrials.gov, all trials with results were closed trials; nevertheless, we found additional publications on PubMed for 15 interventional not closed studies (seven ongoing trials, one not yet recruiting, two withdrawn and five unknown status)