Ventilation defects on hyperpolarized helium-3 MRI in asthma are predictive of 2-year exacerbation frequency.

Background There is an unmet need for an objective biomarker to predict asthma exacerbations. Objective Here, we assess the ventilation defect percent (VDP) on hyperpolarized (HP) 3He MRI as a predictor of exacerbation frequency following imaging. Methods Subjects underwent HP 3He MRI and conventional clinical measurements, including pulmonary function tests, during a period of disease stability, and exacerbations were recorded prospectively over the following two years. We used a Poisson regression tree model to estimate an optimal VDP threshold for classifying subjects into high versus low exacerbation groups, and then used statistical regression to compare this VDP threshold against conventional clinical measures as predictors of exacerbations. Results Sixty-seven asthmatics (27M 40F, 28 mild/moderate and 39 severe) had median [1Q–3Q] VDP of 3.75% [1.2%–7.9%]. An optimal VDP threshold of 4.28% was selected based on maximum likelihood estimation of the regression tree model. Subjects with VDP > 4.28% (N=32) had a median of 1.5 exacerbations vs. 0.0 for subjects with VDP 4.28% was associated with an exacerbation incidence rate ratio of 2.5 (95% CI 1.3–4.7) vs. VDP Conclusion VDP measured with MRI shows promise as a biomarker of prospective asthma exacerbations.