Multiplex Assays in Allergy Diagnosis: Allergy Explorer 2 versus ImmunoCAP ISAC E112i

ImmunoCAP ISAC E112i (ISAC) and Allergy Explorer 2 (ALEX²) detect specific immunoglobulin E (IgE) reactivity. Both multiplex assays contain molecular allergens and ALEX² additionally includes allergen extracts and inhibitors that block the binding of IgE to cross-reacting carbohydrate determinants (CCDs). This study aimed to compare the performance of ISAC and ALEX² by determining the IgE reactivity against allergen extracts and/or allergen components and by using qualitative, semiquantitative, and quantitative analyses of all comparable allergen components in sera from 216 participants recruited in South Tyrol/Italy. For extract sensitization in ALEX², the analysis revealed negative corresponding allergen components in 18.4% and at least one positive corresponding allergen component in 81.6% of all cases. For ISAC, the corresponding results were 23.5% and 76.5% of cases, respectively. The ALEX² CCD inhibitor eliminated CCD-positive signals detected by ISAC in 88.5% of cases. Based on sensitization values of 0.3–14.9 ISU or kU_A/L, there was good agreement between ALEX² and ISAC, although ALEX² showed higher values than ISAC. The addition of allergen-extract tests in ALEX² resulted in the detection of more sensitizations than with corresponding allergen components alone. In the range of <15 ISU or kU_A/L, ALEX² may be more effective in detecting sensitizations.