D2.38 - Clinical Evaluation of Alternaria alternata Extract Used for Skin Prick Test in Diagnosis of Alternaria alternata Allergy

Alternaria is a common inhalant allergen causing allergic rhinitis and/or asthma, and is widely distributed in both indoor and outdoor environments across northern and southern China. However, China has long relied on using serum-specific IgE detection and intradermal testing. There is a lack of clinically reliable Alternaria skin prick test (SPT) preparation. This study evaluated the accuracy and safety of an Alternaria allergen extract (Alt a 1 0.3mg/ml) for diagnosing Alternaria allergy using the SPT in Peking Union Medical College Hospital (PUMCH).

A total of 910 subjects, who were diagnosed with allergic diseases at the Allergy Department outpatient clinic of PUMCH between August 10, 2015 and August 30, 2017, were consecutively enrolled. All patients were prescribed SPT with Alternaria alternata Extract, and the mean wheal diameter (MWD) was measured. Meanwhile, serum-specific immunoglobulin E (sIgE) to Alternaria alternata was detected by fluorescent enzyme immunoassay. Receiver operating characteristic curve (ROC) analysis was performed based on the results of sIgE value. The accuracy of SPT in Alternaria alternata allergy was evaluated under different diagnostic cutoff points. The safety was assessed by monitoring and recording adverse reactions.

No drop-out cases were reported in this study. The number of subjects in the save set (SS), full analysis set (FAS), and per protocol set (PPS) was 910, 757, and 612, respectively. The elimination rate was 32.75% (298/ 910). The area under the ROC curve of FAS was 0.854 (95% CI: 0.817- 0.873), which of PPS was 0.884 (95% CI: 0.830, 0.939). In PPS, the optimal diagnostic cut-off point for diagnosing Alternaria alternata allergy using SPT was an average wheal diameter of 3.30 mm, with a sensitivity of 79.24% (95% CI: 75.08% - 83.40%) and a specificity of 87.55% (95% CI: 83.29% - 91.81%). The diagnostic cutoff for 95% specificity was an MWD of 3.80 mm. There was no adverse event that occurred in the SS.

This allergen extract of Alternaria alternata demonstrates high specificity and safety in the SPT, while its sensitivity could be optimized by improving the quality of the extract.