Evaluating the diagnostic utility of impulse oscillometry system versus spirometry in diagnosing bronchial asthma among adults in Western India: A diagnostic test accuracy study

BACKGROUND: Bronchial asthma is a chronic inflammatory disorder causing reversible airflow obstruction. Spirometry, the standard diagnostic tool, is effort dependent and challenging for some patients. Recent studies suggest that impulse oscillometry system (IOS) may be more sensitive in detecting early airway impairment than spirometry. However, Indian data comparing IOS with spirometry are limited, and standardized diagnostic cutoff values for IOS in asthma are not well established. AIMS: This study aimed to determine the diagnostic cutoff values of IOS parameters for bronchial asthma and evaluate their utility and association with spirometry and asthma control in the study population. SETTINGS AND DESIGN: This was a cross-sectional, observational, and diagnostic test accuracy study conducted at the department of respiratory medicine of a tertiary care center in Western India. MATERIALS AND METHODS: The study included 100 asthmatic patients (70 previously diagnosed, further classified into well-controlled, partially controlled, and uncontrolled, and 30 newly diagnosed). Spirometry (forced vital capacity [FVC], forced expiratory volume in 1 s [FEV1], and FEV1/FVC) and IOS (R5, R20, X5, and Fres) measurements were performed in all patients. IOS results were compared with spirometric results. STATISTICAL ANALYSIS USED: Descriptive statistics, Pearson correlation analysis, and receiver operating characteristic (ROC) curve evaluation were used to determine the sensitivity, specificity, and diagnostic cutoff values of IOS parameters. RESULTS: IOS detected abnormalities in 61.7% of the participants with normal spirometry. R5, X5, Fres, and AX showed a significant correlation with FEV1 and asthma severity. The study established specific cutoff points for various oscillometry parameters with moderate sensitivity and specificity. CONCLUSION: The study concludes that oscillometry is more sensitive than spirometry in detecting small airway dysfunction in asthma patients.