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Table 2 The characteristics of trials which included SR in the introduction or not included when there was a SR available in the literature within 12 months of trial commencement (N = 220)

From: Are orthodontic randomised controlled trials justified with a citation of an appropriate systematic review?

Variable SR not included but available in literature N (%) (N = 56) SR included N (%) (N = 164) Pearson Chi2 or Fisher’s exact test (p < 0.05)
Year of publication
 2010 2 (25.0) 6 (75.0) 0.75
 2011 3 (37.5) 5 (62.5)  
 2012 4 (40.0) 6 (60.0)  
 2013 2 (20.0) 8 (80.0)  
 2014 4 (33.3) 8 (66.7)  
 2015 5 (27.8) 13 (72.8)  
 2016 8 (40.0) 12 (60.0)  
 2017 5 (17.9) 23 (82.1)  
 2018 5 (16.7) 25 (83.3)  
 2019 7 (22.6) 24 (77.4)  
 2020 11 (24.4) 34 (75.6)  
Journal type
 AJODO 12 (28.6) 30 (71.4) 0.14
 ANGLE 12 (21.1) 45 (78.9)  
 EJO 17 (23.9) 54 (76.1)  
 OCR 4 (25.0) 12 (75.0)  
 AOJ 3 (100.0) 0 (0.0)  
 JOO 2 (28.6) 5 (71.4)  
 JO 6 (25.0) 18 (75.0)  
Continent of corresponding author
 Europe 22 (20.0) 88 (80.0) 0.006
 Americas 5 (14.7) 29 (85.3)  
 Asia or other 29 (38.2) 47 (61.8)  
Ethical approval
 No approval or exempt from approval 5 (35.7) 9 (64.3) 0.36
 Ethical approval obtained 51 (24.8) 155 (75.2)  
 Involvement of statistician
 Not reported 37 (24.5) 114 (75.5) 0.63
 Reported 19 (27.5) 50 (72.5)  
Trial registration
 No 37 (28.0) 95 (72.0) 0.28
 Yes 19 (21.6) 69 (78.4)  
Significance of results
 Not significant 28 (25.5) 82 (74.5) 1.00
 Significant 28 (25.5) 82 (74.5)  
Conflict of interest
 Conflicts exist and declared 33 (26.4) 92 (73.6) 0.85
 No conflicts to declare 22 (24.7) 67 (75.3)  
 Not clearly declared 1 (16.7) 5 (83.3)  
Funding
 Industry funded and declared 19 (20.7) 73 (79.3) 0.23
 No industry sponsorship/funding to declare 30 (31.3) 66 (68.8)  
 Not clearly declared 7 (22.6) 24 (77.4)  
Number of authors
 Median (IQR) 5 (3) 4.5 (3)  
Impact factor
 Median (IQR) 1.96 (0.41) 1.96 (0.47)