| Patient age | All patients | p-value# | ||||
| 3≤24 months | 2–6 years | 7–11 years | 12–18 years | |||
| Patients¶ N | 94 | 134 | 108 | 118 | 456 | |
| ECG | 90 (96) | 127 (95) | 102 (94) | 111 (94) | 430 (94) | 0.42 |
| Chest radiograph | 87 (93) | 115 (86) | 94 (87) | 110 (93) | 406 (89) | 0.02 |
| Echocardiogram | 88 (94) | 129 (96) | 106 (98) | 116 (98) | 439 (96) | 0.58 |
| HC+ | 91 (97) | 132 (99) | 103 (95) | 117 (99) | 445 (98) | 0.25 |
| Holter monitor | 9 (10) | 26 (19) | 21 (19) | 38 (32) | 94 (21) | 0.001 |
| Laboratory function tests | 78 (83) | 117 (87) | 103 (95) | 113 (96) | 411 (90) | 0.002 |
| 6-min walk test§ | 0 | 32 (24) | 59 (55) | 84 (71) | 175 (38) | <0.001 |
| Cardiopulmonary exercise test | 0 | 3 (2) | 12 (11) | 19 (16) | 34 (7) | <0.001 |
| Pulmonary function tests | 2 (2) | 16 (12) | 40 (37) | 64 (54) | 122 (27) | <0.001 |
| Overnight oxygen saturation and sleep recording | 31 (33) | 45 (34) | 23 (21) | 30 (25) | 129 (28) | 0.10 |
| Lung perfusion scintigraphy | 11 (12) | 27 (20) | 28 (26) | 38 (32) | 104 (23) | 0.004 |
| Pulmonary angiography | 42 (45) | 61 (46) | 45 (42) | 50 (42) | 198 (43) | 0.89 |
| Chest computed tomography | 36 (38) | 53 (40) | 46 (43) | 54 (46) | 189 (41) | 0.70 |
| Magnetic resonance imaging | 1 (1) | 4 (3) | 13 (12) | 24 (20) | 42 (9) | <0.001 |
| Lung biopsy | 5 (5) | 8 (6) | 4 (4) | 4 (3) | 21 (5) | 0.75 |
Data are presented as n (%) unless otherwise stated. N: total number of patients; n: all patients who were confirmed as having undergone the procedure. HC: heart catheterisation. #: Fisher's exact test to compare across the age groups for diagnostic procedure being performed; ¶: the exact date of birth could not be obtained for two patients; however, both were in the paediatric age group and included in the general analysis and do not appear in this table; + it was intended that all patients would undergo HC; however, 11 patients had indications on their case-report form that pulmonary hypertension was not confirmed by HC, 10 patients provided no further HC data. §: nine of these patients (2–6 years n = 2; 7–11 years n = 1; 12–8 years n = 6) have Down syndrome or other chromosomal abnormalities. The denominator for percentages was N.