Bronchial allergen challenges in children – safety and predictors

Background In allergic asthma, the diagnosis of house dust mite ( HDM ) allergy is mainly based on the patient's history, allergy testing by the skin prick test ( SPT ) or the levels of allergen‐specific IgE. We retrospectively analysed data from 350 bronchial provocations with HDM and related it to the following parameters: specific IgE, bronchial hyperresponsiveness ( BHR ) to methacholine testing ( MCT ) and exhaled NO ( eNO ). Methods Approximately 350 patients (5–18 yr of age) with allergic asthma and a positive SPT to HDM s were included. To define the sensitivity and specificity for the detection method of an early asthmatic response ( EAR ), a receiver‐operating characteristic ( ROC ) curve was plotted. The accuracy was measured by the area under the ROC curve ( AUC ). A logistic regression model was used to predict the individual probability of a positive challenge. The results of the regression model were validated in a prospective group of n = 75 patients. Results The following cut‐off values showed the best combination of sensitivity and specificity: specific IgE Dermatophagoides farinae 19.6  kU /l ( AUC , 0.88), PD 20 FEV 1 0.13 mg methacholine ( AUC , 0.73) and eNO 20.1 ppb ( AUC , 0.71). The following equation predicted the individual probability of a positive challenge in the retrospective and prospective group: p = 1 . [1 + exp[−(−1.78 + 2.46. 10 log D. far  − 1.25 .10 logPD 20 metha)]] −1 , ( AUC  = 0.88). Conclusions The value of using the specific I g E and MCT as predictors was confirmed in a large number of patients. We also showed, for the first time, that the eNO predicted the EAR . The logistic regression model is repeatable with a good accuracy.