Supplementary Material for: Role of Serum Olfactomedin 4 as a Biomarker in Bronchial Asthma – A Pilot Cross-Sectional Comparative Study

Introduction: Asthma is a heterogeneous chronic airway disease marked by variable airflow limitation and bronchial hyperresponsiveness. While eosinophilic inflammation is well studied, neutrophil-driven and mixed eosinophilic–neutrophilic patterns are increasingly recognized in severe or poorly controlled asthma. Olfactomedin 4 (OLFM4), a neutrophil-expressed glycoprotein involved in immune regulation, has emerged as a potential biomarker of neutrophilic inflammation, though its role in asthma is underexplored. This study aimed to evaluate serum OLFM4 levels in asthma patients and examine their association with disease severity and control. Methods: A pilot cross-sectional, hospital-based comparative study was conducted at JSS Medical College, Mysore, between June 2023 and December 2024. Eighty participants were recruited: 60 asthmatics (20 each with mild, moderate, and severe asthma) and 20 healthy controls. Serum OLFM4 was measured using ELISA. Asthma severity was assessed by spirometry, and asthma control by the Asthma Control Test (ACT). Associations with hematological and pulmonary function parameters were analyzed. Results: Serum OLFM4 levels were significantly higher in asthmatics compared to controls (4309.23 ± 1533.97 vs. 1344.41 ± 256.38 pg/mL; p