Predicting airway hyperresponsiveness to methacholine in patients with atopic dermatitis

Background: There are overlapping physiologic mechanisms between atopic dermatitis (AD) and asthma. However, predictive factors in development of airway hyperresponsiveness (AHR) in patients with AD are lacking. Objective: This study aimed to determine factors predictive of AHR in patients with AD without a history of asthma. Methods: We performed a cross-sectional study measuring methacholine AHR in 12 participants with AD without a history of asthma. The clinical data measured included AD onset and severity. In addition, skin biopsy sample scores, sputum eosinophil counts, blood eosinophil counts, total IgE levels, and spirometry findings were obtained and compared between subjects with and without methacholine AHR. Results: Three of 12 participants with AD had a positive methacholine challenge result. Compared with the participants with AD without AHR, the participants with AD and AHR had significantly higher Eczema Area and Severity Index (EASI) scores (21.5 ± 13.6 vs 3.5 ± 2.9) and blood eosinophil counts (330/μL ± 50 vs 130/μL ± 60) (both P < .05), as well as higher sputum eosinophil counts (3.92% ± 4.6% vs 0.38% ± 0.44%) and total IgE levels (832.3 IU/mL ± 922 vs 109.8 IU/mL ± 79). A lower ratio of FEV₁ value to forced vital capacity (FVC) value (% predicted) (ie, FEV₁/FVC [% predicted]) (80 ± 0.04 vs 86 ± 0.03) was also demonstrated in participants with AHR, with a negative correlation between FEV₁/FVC (% predicted) and blood eosinophil count (r = -0.66 [P = .02]) and EASI score (r = -0.56 [P = .058]). Conclusion: In this small group study, our data show that patients with AD without asthma but with AHR have higher EASI scores, elevated eosinophil counts, and circulating IgE levels, along with lower values of FEV₁/FVC (% predicted).