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Table 3 Study characteristics of the included RCTs

From: Surgical trials and trial registers: a cross-sectional study of randomized controlled trials published in journals requiring trial registration in the author instructions

Study characteristic Registered RCTs (n = 85) Unregistered RCTs (n = 18)
National, multinational setting 68 (80%), 17 (20%) 18 (100%), 0
Monocenter, multicenter setting 49 (58%), 36 (42%) 15 (83%), 3 (17%)
Sample size (median (range)) 126 (12 to 66,000) 66 (12 to 256)
Country of main investigator USA (n = 13), Germany (n = 8), Netherlands (n = 7), China (n = 6), Italy (n = 6), Norway (n = 6), UK (n = 5), Japan (n = 4), Austria (n = 3), Belgium (n = 3), Denmark (n = 3), South Korea (n = 3), Spain (n = 3), Sweden (n = 3), Switzerland (n = 3), Finland (n = 2), Egypt (n = 2), New Zealand (n = 2), and Australia, France, and India (for all n = 1) South Korea (n = 5), USA (n = 5), Brazil (n = 2), UK (n = 2), and China, Finland, India, and Ukraine (for all n = 1)
Surgical subspecialty or surgery-related discipline General surgery (n = 24), endoscopy/gastroenterology/gastrointestinal surgery (n = 14), nephrology/kidney transplantation/surgery (n = 10), bariatric surgery (n = 6), hepatology/liver transplantation/hepatobiliary surgery (n = 6), anesthesiology/surgery (n = 5), pediatrics/pediatric surgery (n = 3), psychiatry/neurology/surgery (n = 5), cardiology/heart transplantation/cardiothoracic surgery (n = 2), colorectal surgery (n = 2), and other (n = 8) General surgery (n = 9), gastroenterology/gastrointestinal endoscopy/gastrointestinal surgery (n = 3), anesthesiology (n = 2), neurosciences/neurology/psychiatry/otolaryngology (n = 2), pediatric surgery (n = 1), and reconstructive breast surgery (n = 1)
  1. RCT, randomized control trial.