# An Assessment of the Currently Available Molecular Assay for the Diagnosis of Anisakis Sensitization

## TL;DR

This study evaluates the ALEX-2 test for diagnosing Anisakis allergy and finds it may not be sensitive enough for first-line use but could provide useful additional insights.

## Contribution

The study introduces the evaluation of ALEX-2 for Anisakis sensitization and highlights the clinical relevance of Ani s 1 and Ani s 3 allergens.

## Key findings

- ALEX-2 showed 39.39% positivity for Ani s 1 or Ani s 3 in confirmed Anisakis cases.
- Ani s 3 levels correlated with the severity of allergic reactions (r = 0.31, p = 0.01).
- The test may not be sufficiently sensitive for first-line diagnosis but could offer additional diagnostic value.

## Abstract

The diagnosis of allergic reactions to Anisakis remains challenging due to the lack of specific allergens available for routine clinical use. However, the latest version of the multiplex macroarray ALEX-2 now allows the detection of specific IgE against Ani s 1, the major species-specific allergen, as well as Ani s 3 (tropomyosin), a highly cross-reactive molecule with homologs in other allergenic sources. This study aimed to evaluate the potential role of ALEX-2 in diagnosing Anisakis sensitization by comparing it with a previously validated diagnostic algorithm. Serum samples from patients with suspected Anisakis sensitization were consecutively collected at an Italian allergy centre. Diagnosis was based on a history of allergic reactions following seafood consumption, along with negative test results for fish allergy. All patients underwent skin prick testing and specific IgE measurement for Anisakis (p4), Ascaris (p1), shrimp (f24), and Dermatophagoides pteronyssinus (d1), as well as tropomyosins from house dust mites (d205) and shrimp (f351). Additionally, the basophil activation test (BAT) using crude Anisakis extract was performed. Patients were also tested using the ALEX-2 allergy macroarray. Correlation analyses and multiple logistic regression models were applied to assess associations between conventional singleplex tests and the severity of clinical manifestations. A total of 33 eligible subjects were recruited, including 20 females (60.6%). Seven (21.2%) were aged 0–29 years, eleven (33.3%) were 30–60 years old, and fifteen (45.5%) were over 60 years old. ALEX-2 showed positivity for Ani s 1 or Ani s 3 in 39.39% (95% CI: 22.90–57.86%) of subjects with confirmed Anisakis sensitization. A significant correlation was observed between Ani s 3 (r = 0.31 [95% CI: 0.04–0.56], p = 0.01) and Ascaris (r = 0.35 [95% CI: 0.129–0.55], p = 0.004) levels and the severity of clinical reactions. Despite the limitations of this cross-sectional study, including a small sample size, our preliminary findings suggest that the ALEX-2 macroarray may not be sufficiently sensitive for the first-line diagnosis of Anisakis allergy. However, it could provide valuable additional information, as Ani s 1 positivity indicates primary sensitization to the nematode, while Ani s 3 positivity appears to correlate with clinical severity. Larger prospective longitudinal studies are needed to confirm these findings and further assess the predictive value of ALEX-2 in diagnosing Anisakis allergy.