Clinical Evaluation of an Alternaria alternata Extract Used for Skin Prick Test in Diagnosing

\articletype Original Articles Background: Alternaria alternata is a major fungal allergen, yet standardized skin prick test (SPT) extracts are lacking in China, hindering the use of this simple, first-line diagnostic tool. This study aimed to clinically evaluate a novel, domestically developed A. alternata extract for SPT and establish a diagnostic cutoff in a Chinese population. Methods: In this prospective, single-center study, 910 patients with allergic diseases were consecutively enrolled. All underwent SPT with the in-house A. alternata extract (Alt a 1: 25.7–34.8 µg/mL). Serum-specific IgE (sIgE) (ImmunoCAP™) served as the reference standard. Diagnostic accuracy was analyzed using receiver operating characteristic (ROC) curves. Safety was assessed by monitoring adverse events. Results: The per-protocol set included 610 subjects. The area under the ROC curve was 0.868 (95% CI: 0.839–0.897). The optimal diagnostic cutoff was a mean wheal diameter of 3.25 mm, yielding a sensitivity of 79.32% (95% CI: 74.46%–84.18%) and specificity of 86.11% (95% CI: 82.35%–89.87%). To achieve 95% specificity, the cutoff increased to 4.25 mm. No adverse events were reported among all 910 participants. Conclusion: The novel A. alternata SPT extract demonstrates high diagnostic accuracy and an excellent safety profile. The established cutoff of 3.25 mm provides a population-optimized threshold for clinical diagnosis in China. This study addresses a critical gap in allergen standardization and supports the adoption of SPT as a reliable, first-line diagnostic tool for fungal allergy in clinical practice.