Table 1

Characteristics of workers with occupational asthma with and without sputum eosinophilia

With sputum eosinophilia (n=14)Without sputum eosinophilia (n=24)p value
Figures are mean (SD) or median (interquartile range) except where stated. NSBR=non-specific bronchial reactivity. Subjects with PD20 >4800 μg were arbitrarily given a value of 9600 μg methacholine. Atopy was defined as ≥3 mm skin prick test reaction to one or more common aeroallergens.
Diagnosis confirmed by specific challenge tests39
Median Oasys-2 score (interquartile range)2.83 (2.55–3.2)3.23 (2.88–3.76)
% with increased NSBR at presentation92.9500.012*
>3.2-fold change in NSBR in relation to workplace exposure2/41/1
Age (years)46.8 (12.1)44.8 (7.1)0.52
Atopic subjects (%)64.362.51.0
% on inhaled corticosteroids85.745.80.02*
Current/ex/never smokers (%)35.7/28.6/35.733.3/8.3/58.3
≥10 pack year smoking history (%)57.129.20.17
Latent interval between first exposure and symptom onset, median (years)6.8 (1.5–11.7)2.8 (0.6–7.6)0.29
Duration of symptomatic exposure, median (years)3.3 (1.7–5.6)3.6 (2.0–6.7)0.57
Total duration of exposure, median (years)10.8 (3–16.3)7.1 (3.5–16.9)0.86
PEF variability (% predicted)12.9 (6.5)14.2 (6.1)0.55
Mean rest – mean work PEF difference (l/min)36.4 (26.1)30.5 (18.2)0.42
Mean maximum rest PEF minus mean minimum work PEF (as % max PEF), median19.0 (12.9–29)16.7 (12.8–21.7)0.55
Pre-bronchodilator FEV1 (% predicted)61.4 (21.2)83 (16)0.001*
Pre-bronchodilator FEV1/FVC (%)61.4 (14.2)70.2 (8.2)0.02*
Bronchodilator reversibility (absolute value in ml)397 (265)161 (197)0.003 *
Methacholine PD20 μg, geometric mean (interquartile range)253 (75–1048)1401 (545–8362)0.007*
Total SGRQ score57 (11.7)44.4 (16.1)0.016 *
Exhaled nitric oxide (NO) ppb, geometric mean (interquartile range)10.4 (5.6–17.4)5.1 (3.7–6.6)0.001*
Subjects with raised NO >9.6 ppb (%)64.34.2<0.001*
Sputum eosinophils (median %)6.50.3
Sputum neutrophil count (%)59.5 (19.6)55.1 (18.8)0.5
Sputum macrophage (%)24.6 (9)43.2 (19.2)0.002*
Total cell count (×106/mg sputum)3.3 (3.1)3.7 (3.3)0.72