Thunderstorm asthma in seasonal allergic rhinitis: The TAISAR study

Background Asthma epidemics associated with thunderstorms have had catastrophic impacts on individuals and emergency services. Seasonal allergic rhinitis (SAR) is present in the vast majority of people who develop thunderstorm asthma (TA), but there is little evidence regarding risk factors for TA among the SAR population. Objective We sought to identify risk factors for a history of TA and hospital presentation in a cohort of individuals with SAR. Methods This multi-centre study recruited adults from Melbourne (Australia) with a past diagnosis of TA and/or self-reported SAR. Clinical information, spirometry, white blood-cell count, ryegrass pollen specific IgE (RGP-spIgE) and fractional exhaled nitric oxide (FeNO) were measured to identify risk factors for a history of TA in individuals with SAR. Results From a total of 228 individuals with SAR, 35% (80/228) reported SAR only (I-SAR), 37% (84/228) reported TA symptoms but had not attended hospital for treatment (O-TA) and 28% (64/228) had presented to hospital for TA (H-TA). All H-TA patients reported a previous asthma diagnosis. Logistic regression analysis of factors associated with O-TA and H-TA indicated that lower forced expiratory volume in one second (FEV1) and asthma control questionnaire (ACQ) score >1.5 were associated with H-TA. Higher blood RGP-spIgE, eosinophil counts, and FeNO were significantly associated with both O-TA and H-TA. Receiver-operating curve (ROC) analysis showed RGP-spIgE >10·1 kU/L and pre-bronchodilator FEV1 ≤90% to be biomarkers of increased H-TA risk. Conclusion Clinical tests can identify risk for a history of TA in individuals with SAR and thereby inform patient-specific treatment recommendations.