Serum Level of Eosinophil Cationic Protein in Patients with Chronic Cough: Relationship to Blood Eosinophils and Airway Hyperresponsiveness

Abstract

We measured the serum level of eosinophil cationic protein (ECP), determined the blood eosinophil count, and assessed pulmonary function by spirometry and airway responsiveness to methacholine in 80 patients with a cough lasting longer than 3 weeks without an obvious cause. The serum level of ECP was above the cutoff value of 15.7 ng/mL (mean + 2 SD in 105 healthy control adults) in 30 (37.5%) of 80 patients (high-serum-ECP group). The blood eosinophil count was significantly higher in the high-serum-ECP group than in the normal-serum-ECP group (p < 0.01). The cumulative dose of methacholine causing a 35% decrease in respiratory conductance (PD₃₅Grs) was significantly lower in the high-serum-ECP group than in the normal-serum-ECP group (p < 0.001). The serum concentration of ECP was correlated with the blood eosinophil count and the PD³⁵ Grs (r = 0.59, p < 0.001 and r = -0.48, p < 0.001, respectively). These findings suggest a possible role for serum level of ECP in management of patients with chronic cough. (p < 0.001). The serum concentration of ECP was correlated with the blood eosinophil count and the PD₃₅Grs (r = 0.59, p < 0.001 and r = -0.48, p < 0.001, respectively). These findings suggest a possible role for serum level of ECP in management of patients with chronic cough.

Key Words:

• Eosinophil cationic protein
• Eosinophil
• Chronic cough
• Bronchial asthma
• Cough variant asthma
• Eosinophilic bronchitis
• Airway hyperresponsiveness