Identification of clusters of asthma control: A preliminary analysis of the Inspirers studies

Abstract

Aims: To identify distinct asthma control clusters based on Control of Allergic Rhinitis and Asthma Test (CARAT) and to compare patients’ characteristics among these clusters. Methods: Adults and adolescents (≥13 years) with persistent asthma were recruited at 29 Portuguese hospital outpatient clinics, in the context of two observational studies of the INSPIRERS project. Demographic and clinical characteristics, adherence to inhaled medication, beliefs about inhaled medication, anxiety and depression, quality of life, and asthma control (CARAT, >24 good control) were collected. Hierarchical cluster analysis was performed using CARAT total score (CARAT -T). Results: 410 patients (68% adults), with a median (percentile 25–percentile 75) age of 28 (16­‑46) years, were analysed. Three clusters were identified [mean CARAT -T (min -max)]: cluster 1 [27(24 -30)], cluster 2 [19(14 -23)] and cluster 3 [10(2 -13)]. Patients in cluster 1 (34%) were characterised by better asthma control, better quality of life, higher inhaler adherence and use of a single inhaler. Patients in clusters 2 (50%) and 3 (16%) had uncontrolled asthma, lower inhaler adherence, more symptoms of anxiety and depression and more than half had at least one exacerbation in the previous year. Furthermore, patients in cluster 3 were predominantly female, had more unscheduled medical visits and more anxiety symptoms, perceived a higher necessity of their prescribed inhalers but also higher levels of concern about taking these inhalers. There were no differences in age, body mass index, lung function, smoking status, hospital admissions or specialist physician follow -up time among the three clusters. Conclusion: An unsupervised method based on CARAT- -T, identified 3 clusters of patients with distinct, clinically meaningful characteristics. The cluster with better asthma control had a cut -off similar to the established in the validation study of CARAT and an additional cut -off seems to distinguish more severe disease. Further research is necessary to validate the asthma control clusters identified.