Baseline characteristics of children with spirometry and FeNO data (n=465)
| Males (%) | 249 (54) |
| Mean age in years (95% CI, range) | 10.9 (10.7 to 11.2, 5–16) |
| Median deprivation decile of patients according to registered practice (IQR) | 4 (4 to 6) |
| Mean BMI (95% CI, range) | 19.7 (19.3 to 20.1, 11.3–42.6) |
| Number (%) of children with BMI: | |
| ≤2nd centile (underweight) | 12 (2) |
| >2nd to <91st centile (healthy) | 426 (70) |
| ≥91st to <98th centile (overweight) | 80 (13) |
| ≥98th centile (obese) | 93 (15) |
| Number (%) of children identifying as each ethnic category: | |
| White | 365 (78) |
| Black | 16 (3) |
| Asian | 63 (14) |
| Mixed | 21 (5) |
| Median ACT score in children >11 years (IQR) | 20 (17–23) |
| Median CACT score in children ≤11 years (IQR) | 21 (17–24) |
| Number of children with ACT/CACT <20 (%) | 191 (41) |
| No. of children with ≥1 asthma attacks in preceding 6 months (%) | 103 (22) |
| No. of children prescribed ≥1 inhaled corticosteroid in preceding 6 months (%) | 252 (54) |
| No. of children prescribed ≥1 SABA inhaler in preceding 6 months (%) | 332 (71) |
| No. of children prescribed no ICS or SABA in preceding 6 months (%) | 106 (23) |
| Mean asthma medication ratio in children in preceding 6 months (95% CI, range) | 0.53 (0.49 to 0.56, 0–1) |
| Mean FEV1 z-score (95% CI) | −0.5 (−0.6 to −0.3) |
| Mean FEV1/FVC z-score (95% CI) | −0.7 (−0.8 to −0.6) |
| Number of children with FEV1, FVC or FEV1/FVC <LLN (%) | 114 (25) |
| Number (%) of children with: | |
| Only FEV1 <LLN | 10 (2) |
| Only FEV1/FVC<LLN only | 51 (11) |
| Only FEV1 and FEV1/FVC<LLN | 32 (7) |
| Only FVC <LLN | 4 (1) |
| Only FEV1 and FVC <LLN | 13 (3) |
| FEV1 and FEV1/FVC and FVC <LLN | 4 (1) |
| Median FeNO (ppb) (IQR) | 23 (11–53) |
ACT, asthma control test; BMI, body mass index; CACT, childhood asthma control test; FeNO, fraction of exhaled nitric oxide; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; ICS, inhaled corticosteroids; LLN, lower limits of normal; SABA, short acting beta-2 agonist.