Impact of CCD Inhibition on Semi-Quantitative Multiple Allergen Simultaneous Test

Background/Objectives: Cross-reactive carbohydrate determinants (CCDs) are a well-recognized source of false-positive results in allergen-specific IgE assays, leading to overestimation of polysensitization. This study aimed to evaluate the impact of CCD inhibition on semi-quantitative multiple allergen simultaneous test (MAST) using the AdvanSure™ AlloScreen Max108 Panel (LG Chem, Seoul, Republic of Korea). Methods: We analyzed 65 serum samples positive for anti-CCD IgE (class ≥ 1). A total of 6624 allergen-specific IgE results across foods, pollens, mites, animal epithelia, and fungi were compared before and after CCD-blocker (20 µg) pretreatment. Results: After CCD-blocker pretreatment, a total of 1686 allergen-specific IgE results converted from positive to negative out of 2631 positives before inhibition (overall conversion rate 64.1%). The reversion to negative rate declined progressively with increasing MAST class (p < 0.0001 for trend). By allergen group, CCD-blocker pretreatment reduced IgE positivity from 28.2% to 8.1% in foods, from 70.1% to 23.3% in pollens, and from 41.0% to 29.2% in mites (all p < 0.001), whereas animal epithelia and fungi exhibited minimal or no significant inhibition. Notably, while CCD antigens themselves exhibited class-dependent conversion rates, non-CCD allergens did not show significant differences by CCD class. In venom allergens, honey bee and yellow jacket IgE levels decreased significantly, with resolution of double-positivity in 94.1% of cases. In the dose-response analysis, increasing the CCD-blocker concentration from 20 µg to 40 µg yielded additional inhibition in selected pollens and foods, while most other allergens showed minimal incremental change. Conclusions: CCD inhibition markedly improves the specificity of MAST by reducing false-positive results, particularly in food and pollen allergens.