# Profiles of apple allergen components and its diagnostic value in Northern China

## TL;DR

This study examines apple allergen profiles in northern China and finds Mal d 1 is the key allergen for diagnosing apple allergy.

## Contribution

The study identifies Mal d 1 as the most effective allergen for diagnosing apple allergy in northern China.

## Key findings

- Mal d 1 showed the highest diagnostic accuracy for apple allergy with an AUC of 0.902.
- Mal d 3 sensitization was linked to mugwort allergy and higher risk of generalized allergies to other foods.
- No allergens effectively distinguished between oral allergy symptoms and generalized symptoms.

## Abstract

Limited is known on the profiles of apple allergy in China.

To explore the clinical significance of apple allergen components in northern China.

This study recruited 40 participants and categorized into apple tolerance (n = 19) and allergy (n = 21) group. The latter was categorized into oral allergy symptoms (OAS, n = 14) and generalized symptoms (GS, n = 7). All participants underwent ImmunoCAP screening to assess sIgE levels of birch, apple, and their components.

The sensitization rates were 90% for Bet v 1, 85% for Mal d 1, 35% for Bet v 2, and 20% for Mal d 3. The overall positive rate for apple allergens was 97.5%, with half demonstrating mono-sensitization to Mal d 1. Birch, Bet v 1 and Mal d 1 sIgE levels had consistent areas under the curve (AUC 0.747, p = 0.037; AUC 0.799, p = 0.012; AUC 0.902, p < 0.001 respectively) in diagnosing apple allergy. The optimal cut-off values were determined to be 22.85 kUA/L (63.6% sensitivity, 85.7% specificity), 6.84 kUA/L (81.8% sensitivity, 71.4% specificity) and 1.61 kUA/L (93.8% sensitivity, 75.0% specificity), respectively. No allergens or components demonstrated diagnostic value in distinguishing between OAS and GS. Mal d 3 sensitization was correlated with mugwort allergy and higher risk of peach, nuts or legumes generalized allergy.

Mal d 1 was major allergen and the best for diagnosing apple allergy. Mal d 3 does not necessarily indicate severe allergic reaction to apples in northern China but may indicate mugwort sensitization and an increased risk of peach, nuts or legumes allergy.