PURPOSE: Evaluate respiratory impairment and determine associated sputum and blood markers in those with Western red cedar asthma (WRCA) who have left the exposure setting.
METHODS: Subjects previously diagnosed with WRCA by specific inhalational challenge were invited for followup. They completed a questionnaire and had spirometry and methacholine challenge testing; PC20 to methacholine was determined. Peripheral blood and induced sputum were collected. Sputum cellularity was determined manually after cytospin; Th1/Th2 cytokines concentrations in peripheral blood were determined using the MesoScaleDiscovery platform. The ATS asthma impairment class (IC; a composite of scores derived from FEV1, PC20 and the use of medications) was determined and appropriate multivariate analyses were performed to determine its relationship with sputum cell counts and serum cytokines.
RESULTS: 41 males (mean age 61) who were no longer exposed to WRC returned for followup, at a mean interval of 25 years from initial diagnosis. 49% of these were in IC 0/1 and 51% were in IC 2/3. On average, the PC20 increased by 1.1 mg/ml and the FEV1 decreased by 0.7 L. Mean IL10, IL12, IL13, IL2, and IL4 were each (non-significantly) associated with higher IC. Higher IC was strongly associated with serum IFN-gamma (mean = 1.5 pg/ml in class 2/3 versus 0.6 pg/ml in class 0/1, p=0.008), mainly due to the FEV1 component (correlation with IFN-gamma = -0.46, p=0.005), and with percent sputum eosinophils (mean = 1.2 in class 2/3 versus 0.1 in class 0/1, p=0.007).
CONCLUSION: Ongoing impairment associated with WRCA is related to circulating IFN-gamma, the canonical Th1 cytokine, and sputum eosinophilia.
CLINICAL IMPLICATIONS: Even years after cessation of exposure, patients with WRCA had persistent inflammation characterized by eosinophilia and IFN-gamma.
DISCLOSURE: Chris Carlsten, No Financial Disclosure Information; No Product/Research Disclosure Information