A retrospective observational study on pheno-endotypes of severe asthma among adults attending asthma clinic in a tertiary care centre in India.

Background and Objective: Severe asthma phenotyping based on invasive and non-invasive bio-markers assists in a better understanding of heterogeneity of clinical presentations and thereby using targeted therapies. Therefore, the current study was conducted to evaluate phenotypes based on non-invasive bio-markers of severe asthma patients attending a tertiary care hospital in North India. Methods: This was a retrospective, observational study conducted on the patients who visited the respiratory department of a tertiary care hospital in North India. Patients aged 18 years and above diagnosed with severe asthma were classified into distinct phenotypes, namely, atopic asthma, eosinophilic asthma, and Type 2 low asthma. Patients with their clinical and functional parameters were classified based on the levels of bio-chemical and hematological results [such as total/specific IgE, blood absolute eosinophil count (AEC)], skin prick tests, history of allergy, and the presence of allergic symptoms. Results: Out of total 100 severe asthmatics, the majority of the patients had an eosinophilic asthma (49%) phenotype, followed by atopic (allergic) asthma (36%) and Type 2 low asthma (15%) phenotypes. However, it was found that 29% of these patients had overlap of both atopy and eosinophilia. The atopic phenotype showed allergic symptoms, positive skin prick tests, and elevated IgE levels. The eosinophilic phenotype had high AEC (≥300 cells/uL) and low IgE (< 30 IU/ml) levels. The Type 2 low phenotype showed low AEC and IgE levels along with the absence of allergic symptoms. However, among these 100 patients, overlapping traits of both atopy and eosinophilia were labelled as overlap phenotypes. 50% of type 2 low severe asthma cases had eosinophils >150 cells/cmm and were eligible for mepolizumab. Conclusions: Identification of severe asthma pheno-endotypes based on simple non-invasive bio-markers is feasible in Indian settings, and it is of utmost importance for future treatment planning in these patients with available biologicals. Overlap of eosinophilic and atopic endotypes in one-third cases would challenge physicians to choose upfront appropriate biologicals in our country. Type 2 low asthma was least common with only <10% cases of severe asthma being ineligible for any biological.