Objective: Asthma exacerbations are often triggered by viral respiratory tract infections in children. The aim of the present study was to determine the interaction between asthmatic attacks triggered by viral upper respiratory tract infections and other identified factors on the number of eosinophils, serum eosinophilic cationic protein (ECP) and ECP/eosinophil ratios.

Materials and Methods: Nasal mucosal swabs were obtained on the first admission from children who were hospitalized in the allergy department due to asthmatic attacks with upper respiratory tract infection symptoms, in order to determine viral causative agents. To determine the viral causative agents, viral studies were performed on the samples obtained. Eosinophil count, ECP, and ECP/eosinophil ratios were measured from the blood samples taken immediately on admission. The results were compared to determine the effects of asthmatic attacks, viral factors, drugs, and environmental exposures such as smoking on these values.

Results: Forty-two patients who fulfilled the study criteria were enrolled into the study. While respiratory syncytial virus (RSV) was primarily identified as the causative agent, influenza A/H3N2 and parainfluenza type 3 were determined as the other viral causative agents in 13 (33.3%) of 42 patients. RSV, with 9 cases, was the most frequently identified viral agent in all types of asthma attacks. There was a positive correlation between ECP values and number of eosinophils. There were no significant effects on the number of eosinophils, ECP levels or ECP/eosinophil ratio according to factors such as attacks due to viral infection, allergen sensitivity, usage of prophylactic medications, smoking exposure, and severity of attacks.

Conclusion: In children, asthma attacks are triggered by viral factors, especially RSV. During the attack period, the severity and causes of the attacks had no significant impact on inflammatory markers such as ECP levels, number of eosinophils, and ECP/eosinophil ratio. Furthermore, allergen sensitivity, prophylactic medications and smoking exposure do not affect these levels.