Long-Term Follow-Up of Cluster-Based Diisocyanate Asthma Phenotypes.

Abstract Background Data on the outcome of occupational asthma (OA) are heterogeneous. Objective To assess the impact of being part of a specific cluster at diagnosis on the long-term outcome of diisocyanate-induced OA. Methods We collected data from 56 patients who had a diagnosis of OA confirmed by a positive Specific Inhalation Challenge (SIC). Patients sensitized to toluene diisocyanate (TDI) were allocated to Cluster 1 or 2 based on a tree analysis, using the three variables relevant for cluster segregation identified in a previous study (Mason et al. J Allergy Clin Immunol. 2018): age, BMI, and FEV1/FVC% at diagnosis. Patients sensitized to methylene-diphenyl diisocyanate (MDI) were allocated to Cluster 3, as in previous study. We defined OA remission when a patient had met a total of three criteria: no asthma symptoms and no anti-asthma therapy for the last year, as well as having normal lung function. Results At follow-up, 16 patients showed OA remission. They exhibited better lung function, less bronchial hyperreactivity as well as younger age at diagnosis. Twenty-eight patients were allocated to Cluster 1, 10 to Cluster 2, and 18 to Cluster 3. The percentage of patients with OA remission was higher in Cluster 2 (50% vs 25% in Cluster 1 and 22.5% in Cluster 3), although the difference was not statistically significant (p=0.2789). Conclusions Age at diagnosis was a strong predictor of OA remission. The outcome of diisocyanate OA tended to be more favourable for patients with TDI-OA allocated in Cluster 2, but this finding needs to be validated by further data.