COMPARISON OF SPUTUM-ECP LEVELS IN BRONCHIAL-ASTHMA AND CHRONIC-BRONCHITIS

Eosinophil cationic protein (ECP) is a cationic protein secreted by eosinophils with toxic properties for the respiratory epithelium. Sputum-ECP levels have been shown to correlate inversely with airflow obstruction in asthma. In the present study we investigated whether ECP concentrations are different between asthmatic patients and patients with chronic bronchitis. Sputum-ECP concentrations from seven patients with bronchial asthma and seven patients with chronic bronchitis matched for FEV(1) were compared (FEV(1 Asthma) : 66.1+/-29.0% of predicted; FEV(1 Chronic Bronchitis) : 65.2+/-33.3% of predicted; p = n.s.). Furthermore, sputum-ECP levels in 4 asthmatic patients with severe airflow obstruction and in 1 patient with chronic bronchitis were measured before and after initiation of a 7-day oral therapy with methylprednisolone 20 mg BID. Changes in sputum-ECP values were compared with changes in FEV(1) in these 5 patients. Sputum-ECP levels and pulmonary function were measured as previously described (Am Rev Respir Dis 1992: 145: 604). Sputum-ECP levels from asthmatics were significantly elevated compared with patients with chronic bronchitis: asthma: 893.4+/-346.2 mu g/l per g sputum; chronic bronchitis: 30.0+/-8.5 mu g/l per g sputum (p = 0.002). The degree of airway obstruction correlated with the sputum-ECP levels in asthmatics (r = -0.76, p = 0.05), but not in the patients with chronic bronchitis (r = 0.24, p = n.s.). In a separate group of 4 patients with asthma, elevated sputum-ECP levels prior to initiation of systemic corticosteroid therapy were associated with a marked improvement in FEV(1) after treatment, though this was not observed in one patient with chronic bronchitis and low sputum-ECP levels. We conclude that airflow obstruction in bronchial asthma, but not chronic bronchitis, is associated with elevated sputum-ECP concentrations. Furthermore, preliminary data suggest that elevated sputum-ECP levels predict reversibility of airflow obstruction with systemic corticosteroid therapy. Hence, sputum-ECP levels might be helpful in the differential diagnosis and treatment strategies of bronchial asthma and chronic bronchitis, especially in those patients who lack significant peripheral blood- or sputum-eosinophilia.