Characterization and cluster analysis of Indian adults with asthma in the Vellore district

There is a huge burden of asthma in India, with an estimated 34.3 million patients comprising 13% of the global burden. Little is known about asthma phenotypes, endotypes, and clusters among native Indian patients.

We sought to describe asthma phenotypes and clusters in a specialist outpatient service in Vellore, India.

Systematic assessment was conducted according to Global Initiative for Asthma 2021 guidelines. Data on demographics, types of indoor pollution exposure, comorbidities, skin tests to aeroallergens, spirometry, fractional exhaled nitric oxide, blood eosinophils, total IgE, and percentages of sputum eosinophils and sputum neutrophils were captured prospectively. Descriptive statistics were generated and latent cluster analysis undertaken.

The study included 125 people with asthma (mean ± SD): 58 men aged 47.6 ± 15 years and 67 women aged 42.8 ± 11 years. Three overlapping clusters were identified: cluster 1, highest sensitization to aeroallergens and moderate to severe asthma; cluster 2, modest to moderate rate of aeroallergen sensitization, and moderate to severe asthma; and cluster 3, modest to moderate rate of sensitization to aeroallergens and mild to moderate asthma. Demographic variables, body mass index, age at onset, and other characteristics were comparable between clusters. A weak but significant positive correlation (r = 0.20; P < .05) was detected between sputum and blood eosinophils; there was no correlation between sputum eosinophils and fractional exhaled nitric oxide.

Clinical and physiologic variables and biomarkers indicate that there are overlapping asthma clusters in India's Vellore district. Large multicenter studies are needed to characterize asthma in India and shape national guidelines.