Predictive Factors of the Exacerbation-Prone Phenotype Among Severe Asthmatics in Singapore

Abstract

PURPOSE: Asthma is a heterogenous disease with distinct clinical phenotypes, including the exacerbation-prone phenotype. This subset of patients contributes to disproportionately high morbidity, mortality and healthcare utilization among all asthma patients. We aimed to investigate the factors that are associated with frequent asthma exacerbations in patients with severe asthma. METHODS: 262 patients from the Singapore General Hospital-Severe Asthma Phenotype Study (SGH-SAPS) were screened. These patients fulfilled World Health Organization criteria for “treatment-resistant severe asthma” and were all on combination of high-dose inhaled corticosteroids and long-acting beta-2 agonists. We retrospectively assessed admissions and emergency visits over two years prior to recruitment into the study. 17 patients were excluded from analysis due to incomplete data. The remaining patients were classified as frequent exacerbators if they had > 2 admissions or emergency visits in any one year (n=52). Otherwise, they were classified as non-frequent exacerbators (n=193). Demographic and clinical parameters between the two groups were compared. RESULTS: There was a significantly higher prevalence of eczema, gastro-esophageal reflux disease, anxiety, depression, vocal cord dysfunction and active or past smokers in frequent exacerbators. Frequent exacerbators also had higher body mass index and were more likely to have a history of near-fatal asthma. Multiple logistic regression showed that eczema (odds ratio, OR=5.887), anxiety (OR=8.375) and a history of near-fatal asthma (OR=5.419) were independently associated with the exacerbation-prone phenotype. The number of admissions and emergency visits correlated well with the number of steroid bursts per year. CONCLUSIONS: The frequent asthma exacerbator phenotype was independently associated with the eczema, anxiety and a history of near-fatal asthma.