Mild exacerbations and eosinophilic inflammation in patients with stable, well-controlled asthma after 1 year of follow-up.
OBJECTIVE
To determine the time to exacerbation and probability of a mild exacerbation of asthma, and the impact of eosinophilic inflammation on these parameters in patients with stable, well-controlled asthma.


METHODS
A cohort of 31 patients with stable, well-controlled asthma receiving inhaled steroid treatment regularly were followed up for 1 year or until a mild exacerbation occurred. Mild exacerbation was defined as symptoms of asthma lasting > 48 h with a fall in peak expiratory flow > 20%. FEV(1), provocative concentration of methacholine causing a 20% fall in FEV(1), eosinophil count, and eosinophilic cationic protein (ECP) levels in blood and in sputum were measured at the first visit and every 2 months.


RESULTS
At baseline, the mean (SD) eosinophil count was 0.39 x 10(9)/L (0.21 x 10(9)/L) in blood and 13% (14%) in sputum; ECP was 30 microg/L (28 microg/L) in blood and 75 microg/L (85 microg/L) in sputum. Thirteen subjects experienced a mild exacerbation during the 1-year follow-up period. The mean time to mild exacerbation was 293 days (95% confidence interval [CI], 248 to 337 days), and the cumulative probability of not experiencing a mild exacerbation in 1 year was 49% (95% CI, 39 to 59%). An increased risk of mild exacerbation was associated with blood eosinophil count > 0.4 x 10(9)/L (relative risk 4.5; 95% CI of relative risk, 1.8 to 38.0), blood ECP > 20 microg/L (relative risk, 2.1; 95% CI of relative risk, 1.0 to 9.2), and sputum ECP > 40 microg/L (relative risk, 2.5; 95% CI of relative risk, 1.2 to 11.2), but was unassociated with other variables.


CONCLUSIONS
Patient with stable, well-controlled asthma are at risk of mild exacerbation during 1 year of follow-up despite regular inhaled steroid treatment. Eosinophilic inflammation expressed as eosinophil count and ECP is associated with higher risk of mild exacerbation.
Belda
J
J
Hospital de la Santa Creu i Sant Pau, Barcelona, Catalunya, Spain.
Giner
J
J
Casan
P
P
Sanchis
J
J
D000280:Administration, Inhalation; D000287:Administration, Topical; D000293:Adolescent; D000318:Adrenergic beta-Agonists / Q000008:administration & dosage; D000328:Adult; D000368:Aged; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage; D001249:Asthma / Q000097:blood / Q000188:drug therapy / Q000503:physiopathology*; D001798:Blood Proteins / Q000032:analysis; D001985:Bronchial Provocation Tests; D001993:Bronchodilator Agents / Q000008:administration & dosage; D019819:Budesonide / Q000008:administration & dosage; D047091:Eosinophil Granule Proteins; D004804:Eosinophils / Q000473:pathology*; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume; D005938:Glucocorticoids; D006801:Humans; D007249:Inflammation; D007958:Leukocyte Count; D008137:Longitudinal Studies; D016210:Methacholine Chloride; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate; D012260:Ribonucleases; D012307:Risk Factors
D000318:Adrenergic beta-Agonists; D000893:Anti-Inflammatory Agents; D001798:Blood Proteins; D001993:Bronchodilator Agents; D047091:Eosinophil Granule Proteins; D005938:Glucocorticoids; D016210:Methacholine Chloride; D019819:Budesonide; D012260:Ribonucleases