EVALUATION OF SERUM EOSINOPHILIC CATIONIC PROTEIN AS A MARKER OF DISEASE-ACTIVITY IN CHRONIC ASTHMA

Background: Serum eosinophil cationic protein (ECP) has been promoted as a direct marker of eosinophilic inflammation of the bronchi, especi ally helpful in patients with asymptomatic asthma. Objective: To evalu ate serum ECP against indirect clinical markers of disease activity, w e compared symptom score, bronchial obstruction, bronchial responsiven ess, and blood eosinophil counts with serum ECP levels in children wit h symptomatic and asymptomatic chronic asthma and assessed ECP in othe rs with allergic rhinitis alone. Methods: Twenty-four children with sy mptomatic asthma, 10 children with asymptomatic asthma, and 16 childre n with allergic rhinitis were studied. Measurements were made by stand ardized symptom questionnaire, spirometry, inhalation challenge with h istamine or methacholine, blood eosinophil counts, and radioimmunoassa y of serum ECP. Results: There was no difference in serum ECP levels b etween the symptomatic asthma, asymptomatic asthma, or rhinitis groups , and most values were within the normal range. Activated eosinophil c ounts were higher in subjects with symptomatic asthma than in those wi th asymptomatic asthma but not in subjects with rhinitis. Serum ECP co rrelated with eosinophil counts (p < 0.01) but not symptom score, forc ed expiratory volume in 1 second (FEV(1)), forced expiratory flow, mid -expiratory phase (FEF(25-75)), or provocative concentration causing a 20% fall in FEV(1) (PC20). Symptom scores correlated with PC20 (p < 0 .005) and FEF(25-75) (p < 0.01). Conclusion: Serum ECP is a poor indic ator of disease activity in chronic asthma and cannot differentiate br onchial from nasal inflammation.