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Table 1 Demographic and clinical characteristics of participants and non-participants

From: Factors affecting adolescents’ participation in randomized controlled trials evaluating the effectiveness of healthcare interventions: the case of the STEPSTONES project

Quantitative study Qualitative study
  Participants n = 134 (%) Non-participants n = 223 (%) Statistical test p-value Effect size* Participants n = 10 (%) Non-participants n = 20 (%)
Female sex 61 (45.5) 99 (44.4) X2 = 0.43 p = 0.836 w = 0.02 5 (50) 10 (50)
Distance to hospital (km) 19.9 (IQR = 20.8) 16.5 (IQR = 20.4) Mann-Whitney U = 14,002 z = −0.65 p = 0.516 r = − 0.03
Proportion with cardiac pharmacotherapy 18 (13.4) 34 (16) X2 = 0.344 p = 0.557 w = 0.02
Proportion with special aid in school 5 (4) 13 (5.8) X2 = 1.032 p = 0.31 w = 0.06
Disease complexity**    X2 = 10.195 p = 0.017 w = 0.54   
Mild 14 (10.4) 52 (23.3)     3 (30) 3 (15)
Moderate 84 (62.7) 119 (53.4)     6 (60) 12 (60)
Severe 35 (26.2) 48 (21.5)     1 (10) 5 (25)
Primary diagnosis    Fishers’ exact test = 27.634 p = 0.023 w = 1.46
Single ventricle physiology 5 (3.7) 10 (4.5)      
Tricuspid valve abnormalities 1 (0.7) 4 (1.8)      
Tetralogy of Fallot 15 (11.1) 16 (7.2)      
Double outlet right ventricle 0 (0.0) 10 (4.5)      
Truncus arteriosus 1 (0.7) 2 (0.9)      
Transposition of the great arteries 20 (14.9) 15 (6.7)      
Coarctation of the aorta 25 (18.7) 26 (11.7)      
Atrioventricular septal defect 4 (3.0) 5 (2.2)      
Ebstein anomaly 1 (0.7) 2 (0.9)      
Pulmonary valve abnormalities 15 (11.2) 22 (9.9)      
Aortic valve abnormalities 26 (19.4) 37 (16.6)      
Atrial septal defect 5 (3.7) 16 (7.2)      
Ventricular septal defect 9 (6.7) 30 (13.5)      
Mitral valve abnormalities 3 (2.2) 13 (5.8)      
Pulmonary vein abnormalities 3 (2.2) 9 (4.0)      
Patent ductus arteriosus 1 (0.7) 4 (1.8)      
Other 0 (0.0) 1 (0.4)      
Number of cardiac operations 1.0 (IQR = 2) 1.0 (IQR = 2) Mann-Whitney U = 13,899.500 z = −1.148 p = 0.251 r = −0.06
Number of catheterizations 0.00 (IQR = 0) 0.00 (IQR = 0) Mann-Whitney U= 14,402 z = − 1.08 p = 0.28 r = −0.05
  1. *Cut-offs for Cohen’s w and Cohen’s r = 0.1–0.3 small; 0.3–0.5 = moderate; > 0.5 = large
  2. **Complexity of CHD categorized according to 2018 AHA/ACC Guideline for Management of Adults with Congenital Heart Disease