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

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.

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.

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.

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.

ChiCTR ChiCTR1800014899. Registered 13 February 2018 (retrospectively registered).