COMPARATIVE CROSS-SECTIONAL STUDY OF SPIROMETRY WITH FRACTIONAL EXHALED NITRIC OXIDE (FENO) IN BRONCHIAL ASTHMA PATIENTS AT A TERTIARY CARE CENTRE

Abstract

Background: Bronchial asthma is a heterogeneous inflammatory airway disease requiring accurate phenotyping for optimal management. While spirometry remains the gold standard for assessing airflow limitation, fractional exhaled nitric oxide (FeNO) provides complementary information on eosinophilic airway inflammation. Limited data exist on the correlation between these modalities in Indian tertiary care settings. Objective: To evaluate the correlation between spirometric parameters and FeNO levels in bronchial asthma patients and to assess their combined utility in asthma phenotyping and severity assessment. Methods: This comparative cross-sectional observational study was conducted at Government General and Chest Hospital, Erragadda, Hyderabad, India, over 18 months (2022-2025). One hundred (100) bronchial asthma patients diagnosed according to GINA 2024 criteria underwent comprehensive evaluation including demographic assessment, pre- and post-bronchodilator spirometry, FeNO measurement, and blood biomarker analysis (absolute eosinophil count, neutrophil-lymphocyte ratio). Chi-square test and Pearson correlation analysis were performed to assess associations. Results: The study population (mean age 36.85±11.89 years, 64% female) demonstrated predominantly moderate-to severe airflow obstruction (85%). FeNO levels were low (<25 ppb) in 17%, intermediate (25-50 ppb) in 35%, and high (>50 ppb) in 48% of patients. A highly significant association was observed between spirometric obstruction severity and FeNO levels (χ²=40.86, p<0.00001). Patients with severe obstruction predominantly exhibited high FeNO levels. Peripheral eosinophilia (AEC >300/μL) was present in 49% and showed strong correlation with elevated FeNO (p<0.00001). Overweight/obesity (BMI >25) was present in 38% and associated with severe obstruction in 66% of cases. Conclusion: FeNO demonstrates strong positive correlation with spirometric obstruction severity in bronchial asthma patients. The combined assessment of spirometry and FeNO provides complementary information for asthma phenotyping, particularly in identifying eosinophilic inflammation. This integrated approach supports precision medicine strategies and targeted biologic therapy selection in Indian tertiary care settings.