Pattern of inflammatory phenotypes using sputum cytology among patients with asthma in a tertiary care centre, Kerala –A prospective cohort study

Abstract

Background: Asthma is a chronic inflammatory airway disease in which various inflammatory cells play a pivotal role in pathogenesis. Based on the inflammatory cells count in the sputum, various inflammatory phenotypes are identified. The identification of asthma phenotypes has potential clinical significance, as natural history and treatment response differ according to phenotype.

Objectives: To find out pattern of inflammatory phenotypes of asthma patients and to compare the level of asthma control after 3 months of optimized treatment in different phenotypes.

Methods: We did a hospital based prospective cohort study in the Department of Pulmonary Medicine, Medical College, Thiruvananthapuram, Kerala, over a period of one year. 138 consecutive non-smoker, asthma patients were included. Sputum was examined for differential count .The phenotype was considered eosinophilic if eosinophil count was ≥3% and noneosinophilic if eosinophil count < 3%. Each patient was reassessed after 3 months of optimized treatment and level of asthma control was assessed according to GINA guidelines.

Results: 53.6 % of study population were in the eosinophilic and 46.4 % were in the noneosinophilic phenotype. Mean age of eosinophilic phenotype was 38.4 ± 11.7 years and that of noneosinophilic was 48.8 ± 10.6 years (p<0.001). Mean BMI of eosinophilic asthma patient was 23.3 ± 2.4 and that of noneosinophilic was 24.9 ± 2.3 (p <0.001). Atopic symptoms were present in 73% of the eosinophilic phenotype and 25% of the noneosinophilic phenotype (p<0.001). There was no statistically significant difference between the two phenotypes with regard to the gender, duration of illness, family history of asthma, or initial severity of the disease. After 3 months of optimized treatment, in eosinophilic phenotype 73 % of patients became controlled or partially controlled. In noneosinophilic group only 46.9 % became controlled or partially controlled (p= 0.002).

Conclusion: Noneosinophilic asthma occured in older, obese patients, were usually non atopic and had poor asthma control after three months optimized treatment, compared to eosinophilic phenotype. Thus phenotypic classification could help to guide clinical decisions in personalized medicine approach.