Long-term future risk of severe exacerbations: distinct 5-year trajectories of problematic asthma

Abstract

Background: Assessing future risk of exacerbations is an important component of asthma management. Existing studies have investigated short-, but not long-term risk. Problematic asthma patients with unfavorable long-term disease trajectory and persistently frequent severe exacerbations need to be identified early to guide treatment. Methods: Severe exacerbation rates over five years for 177 "problematic asthma" patients presenting to a specialist asthma clinic were tracked. Distinct trajectories of severe exacerbation rates were identified using group-based trajectory modeling. Baseline predictors of trajectory were identified and used to develop a clinical risk score for predicting the most unfavorable trajectory. Results: Three distinct trajectories were found: 58.5% had rare intermittent severe exacerbations ("infrequent"), 32.0% had frequent severe exacerbations at baseline but improved subsequently ("non-persistently frequent"), and 9.5% exhibited persistently frequent severe exacerbations, with the highest incidence of near-fatal asthma ("persistently frequent"). A clinical risk score composed of ≥2 severe exacerbations in the past year (+2 points), history of near-fatal asthma (+1 point), body mass index≥25kg/m2 (+1 point), obstructive sleep apnea (+1 point), gastroesophageal reflux (+1 point) and depression (+1 point) was predictive of the "persistently frequent" trajectory (area under the receiver operating characteristic curve: 0.84; sensitivity 72.2%, specificity 81.1% using cut-off ≥3 points). The trajectories and clinical risk score had excellent performance in an independent validation cohort. Conclusions: Patients with problematic asthma follow distinct illness trajectories over a period of five years. We have derived and validated a clinical risk score that accurately identifies patients who will have persistently frequent severe exacerbations in the future.