Validity of an Alternaria alternata Skin Prick Test Extract for Diagnosing Sensitization.

Abstract

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.

Objective: This study aimed to clinically evaluate a novel, domestically developed A. alternata extract for SPT and establish a diagnostic cutoff in a Chinese population.

Patients and 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 81.10% (95% CI: 76.76%-85.24%) and specificity of 79.32% (95% CI: 74.46%-84.18%). 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 for detecting Alternaria alternata sensitization and an excellent safety profile. The established cutoff of 3.25 mm provides a population-optimized threshold for identifying sensitized individuals in China. This study addresses a critical gap in allergen standardization and supports the use of SPT as a reliable first-line tool for assessing fungal sensitization in clinical practice.

Trial registration: ChiCTR ChiCTR1800014899. Registered 13 February 2018 (retrospectively registered).