Validation of a Multiplex Assay for Measuring Specific IgG4.

Purpose: Specific IgG4 (sIgG4) increases with allergen specific immunotherapy and may reflect a state of immune tolerance in food allergy. While InununoCAP (R) has been widely used to measure sIgG4 to a single allergen, PROTIATIA (TM) Specific IgG4 (R) has been designed as a multiplex assay for measuring sIgG4. This study sought to validate this assay in comparison to ImmunoCAP (R). Materials and Methods: Measurements of sIgG4 were compared between PROTIA (TM) Specific IgG4 (R) and InununoCAP (R) using sera from 519 allergy patients (asthma: 114, allergic rhinitis: 318, food allergy: 146) with 731 paired tests. sIgG4 was measured against nine inhalant allergens (Dermatophagoides pteronyssinus, Dermatophagoides farinae, cat dander, dog dander, birch pollen, oak pollen, ragweed pollen, mugwort pollen, and Alternaria alternata spores) and nine food allergens (egg white, casein, wheat, peanut, walnut, crab, shrimp, apple, and peach). Results: PROTIAT (TM) Specific IgG4 (R) showed 95.6% agreement rate with InununoCAP (R) in the positivity comparison. For sIgG4 positivity to each individual allergen, an agreement rate of more than 84.8% was observed. In Cohen's kappa analysis, these assays displayed substantial correlations [Cohen's kappa coefficient (x) (kappa) >= 0.699], except for shrimp (kappa=0.448). Furthermore, both assays displayed strong correlations in quantitative comparisons [correlation coefficients value (rho) >= 0.8014], except for apple (rho=0.6571, p=0.175). Serial dilution tests also showed consistency between the assays. Conclusion: FRUITIA (TM) Specific IgG4 (R) showed high consistency with lmmunoCAP (R) in measuring sIgG4. This assay is applicable to various clinical fields, including allergen immunotherapy and food allergy.