Usefulness of induced sputum eosinophil count to assess severity and treatment outcome in asthma patients

CONTEXT: Currently treatment decisions in asthma are governed by clinical assessment and spirometry. Sputum eosinophil, being a marker of airway inflammation, can serve as a tool for assessing severity and response to treatment in asthma patients. AIMS: To establish correlation between change in sputum eosinophil count and forced expiratory volume in one second (FEV(1))% predicted value of asthma patients in response to treatment. In this study, we also predicted prognosis and treatment outcome of asthma patients from baseline sputum eosinophil count. SETTINGS AND DESIGN: A longitudinal study was conducted to determine the treatment outcome among newly diagnosed asthma patients who were classified into A (n = 80) and B (n = 80) groups on the basis of initial sputum eosinophil count (A ≥ 3% and B < 3%). MATERIALS AND METHODS: After starting treatment according to Global Initiative for Asthma Guideline, both A and B groups were evaluated every 15 days interval for the 1(st) month and monthly thereafter for a total duration of 12 months. In each follow-up visit detailed history, induced sputum eosinophil count and spirometry were done to evaluate severity and treatment outcome. RESULTS: FEV(1)% predicted of group A asthma patients gradually increased and sputum eosinophil count gradually decreased on treatment. Longer time was required to achieve satisfactory improvement (FEV(1)% predicted) in asthma patients with sputum eosinophil count ≥3%. There was statistically significant negative correlation between FEV(1)% predicted and sputum eosinophil count (%) in of group A patients in each follow-up visit, with most significant negative correlation found in 8(th) visit (r = −0.9237 and P = < 0.001). Change in mean FEV(1)% (predicted) from baseline showed strong positive correlation (r = 0.976) with change in reduction of mean sputum eosinophil count at each follow-up visits in group A patients. CONCLUSIONS: Sputum eosinophil count, being an excellent biomarker of airway inflammation, can serve as a useful marker to assess disease severity, treatment outcome, and prognosis in asthma patients.