Distinct asthma phenotypes in a multi-ethnic asian population

Background: Phenotyping is the first step towards personalised medicine. Most cluster analyses were performed in predominantly Caucasian populations and amongst the more severe asthmatics. No studies have been performed in an ethnically heterogeneous Southeast Asian cohort. Aim: To determine asthma phenotypes in an ethnically-diverse population in Singapore. Method: Data was collected prospectively from two university-affiliated respiratory specialist clinics. Nine variables: age of asthma onset, gender, smoking status, ethnicity, body mass index (BMI), Asthma Control Test (ACT) score, lung function, number of exacerbations the past year, and blood eosinophil count (BEC) were selected as variables for cluster modelling. Latent class analysis was performed to determine the optimal number of clusters. Results: 437 patients with complete data were included for analysis. A four-cluster model provided the best fit. Validation was performed using discriminant analysis with 94% accuracy on leave-one-out procedure. Cluster 1 was predominantly Chinese (96%), had late onset asthma and mildest disease severity. Cluster 2 was predominantly Malay (75.8%), all patients were obese (BMI ≥30kg/m2), had the lowest BEC and greatest disease severity in terms of inhaled corticosteroid dose, exacerbation rates, lung function and ACT scores. Cluster 3 and 4 were multi-ethnic and had intermediate disease severity. Cluster 3 comprised of female non-smokers but all patients in cluster 4 were smokers and mostly male. Future exacerbation rates did not differ among clusters. Conclusion: This is the first study demonstrating phenotypic differences between Chinese, Malay and Indian asthma patients and to describe the obese asthma cluster in an Asian cohort.