ROC curve analysis of IgE antibodies values to predict clinical allergy to cat dander in asthmatic subjects

Abstract

RATIONALE: Asthmatic patients can be sensitized to cat allergens without clinical allergy symptoms. The aim of this work has been to find an optimal cutoff value for specific IgE predictive of a positive specific bronchial response to cat dander in adult asthmatic patients. METHODS: We performed a bronchial provocation test (BPT) with cat dander (following ATS guidelines) in 72 asthmatic patients (mean age 28.21±10.7, female/male 1.3) with a positive skin prick-test (cat dander 100 BU, ALK-Abelló) and/or detectable cat allergen specific serum IgE (CAP System FEIA). Statistical analyses of results were performed by logistic regression analysis and Receiver Operating Characteristics (ROC) curve. RESULTS: Cat dander BPT was positive in 31 subjects (43%). The area under the ROC curve for CAP values, was 0.838. The optimal cutoff point was 1.6 KU/L (80.6% sensitivity and 72.5% specificity). CAP values of 6.44, 8.26 and 11.75 KU/L showed 90%, 95% and 97.5% specificity, respectively. CONCLUSIONS: In patients with asthma and allergy to cat dander, the determination of specific serum IgE by CAP system is a proper diagnostic test. Quantitative specific IgE levels could be useful to predict clinical allergy.