Prevalence of Airflow Obstruction as Measured by Spirometry, in Rural Southern Indian Adults.

Rural population-based estimates of airflow obstruction based on spirometry are unavailable from southern India. This study assessed the prevalence of spirometry-defined airflow obstruction in Vellore, Tamil Nadu.A cross sectional survey was done in nine villages, among adults aged ≥30 years, where previous cardiovascular surveys had been conducted (1994, 2011). Population proportional to size sampling was used to select 20 clusters, with sampling from all streets proportional to the number of households. One person randomly selected per household was interviewed for symptoms and risk factors. A respiratory therapist performed pre and post bronchodilator spirometry on all, following American Thoracic Society criteria. Airflow obstruction was defined as pre-bronchodilator Forced Expiratory Volume 1 s/Forced Vital Capacity (FEV1/FVC) < Lower Limit of Normal (LLN, derived from local prediction equations) and compared to other criteria.Of 1015 participants, 787 completed technically acceptable spirometry. The prevalence of airflow obstruction was 9.0% (95% CI: 5.8%-9.6%, 71). Fixed obstruction (post bronchodilator FEV1/FVC < LLN) was 4.6% (95% CI: 3.1%-6.1%, 36), and 4.1% (95% CI: 2.7%-5.5%, 32) using post bronchodilator FEV1/FVC < 70%. The GOLD criteria missed 56% (40) of those with airflow obstruction, of which 87.5% were females. Although 63.4% with airflow obstruction had moderate to severe disease, 82.2% were not on treatment and only 48.9% reported symptoms in the previous year.This study estimates prevalence of airflow obstruction based on spirometry in rural southern India. Despite significant impairment on spirometry, majority were undiagnosed, and half did not report symptoms.