TABLE 1. Comparison of Baseline Characteristics in the three Asthma Populations.
| Variable | Primary Care (n = 184) |
Secondary Care (n = 187) |
Longitudinal Cohort (n = 68) |
P Value* |
|---|---|---|---|---|
| Sex, % female | 54.4 | 65.8 | 47.1 | 0.082 |
| Age, yr (SD) | 49.2 (13.9) | 43.4 (15.9) | 52.4 (14.6) | <0.001 |
| Age of onset, yr (SD) | 24.7 (19) | 20.3 (18.4) | 31.1 (23.7) | <0.001 |
| Atopic status, % positive | 72.8 | 73.8 | 57.4 | 0.365 |
| Body mass index, kg/m2 (SD) | 27.5 (5.4) | 28.5 (6.5) | 28.0 (5.9) | 0.55 |
| PC20 methacholine†, mg/ml | 1.04 (1.13) | † | 0.67 (0.68) | 0.19 |
| Peak flow variability, amp % mean | 17 (0.38) | 32.2 (0.48) | 13.8 (0.29) | <0.001 |
| FEV1 change with bronchodilator, % | 1.63 (1.16) | 12.8 (0.41) | 3.2 (1.04) | <0.001 |
| Post-bronchodilator FEV1, % predicted | 91.4 (21) | 82.1 (21.1) | 80.2 (20.6) | 0.013 |
| Sputum eosinophil count, % | 1.32 (0.62) | 2.9 (0.99) | 2.4 (0.81) | 0.08 |
| FeNO‡, ppb | 31.6 (0.33) | 43 (0.32) | 4.32 (0.64)‡ | <0.001 |
| Sputum neutrophil count, % | 55.09 (0.31) | 46.7 (0.32) | 41.1 (0.35) | 0.04 |
| Modified JACS§ (SD) | 1.36 (0.74) | 2.02 (1.16) | 1.42 (1.26) | <0.001 |
| Dose of inhaled corticosteroid, BDP equivalent/μg (SD) | 632 (579) | 1,018 (539) | 1,821 (1,239) | <0.001 |
| Long-acting bronchodilator use, % | 40.2 | 93 | 86.7 | <0.001 |
Definition of abbreviations: amp = amplitude; BDP = beclomethasone dipropionate; JACS = Juniper Asthma Control Score; SD = standard deviation.
Significance figures are derived using one-way analysis of variance between the three populations for continuous variables or χ2 test for proportions.
Bronchial challenge testing is not routinely performed in secondary care for refractory asthma. The comparison given is between the primary-care asthma population and the longitudinal study cohort.
FeNO was measured using the NIOX (Aerocrine, Solna, Sweden) analyzer at 50 ml/second in the primary-care population and secondary-care population. The Logan (Logan Research, Ltd., Rochester, Kent, UK) analyzer was used at a flow rate of 250 ml/second in the longitudinal study cohort. A strong linear correlation of 0.97 exists between the two measurement protocols. The statistical comparison is between Feno levels in primary and secondary care using NIOX.
The Juniper Asthma Control Score, modified to include the symptom domains only (see the online supplement).