A qualitative and quantitative comparison of IgE antibody profiles with two multiplex platforms for component-resolved diagnostics in allergic patients.

Background: Clinically complex phenotypes require more and more sophisticated and comprehensive diagnostic approaches, able to discriminate genuine sensitizations from cross-reactivity. Interpretative complexity of multiplex diagnostic arrays has somewhat limited their diffusion. This study compares two currently available methods, namely ISAC test and ALEX2 test.

Methods: In total, 140 allergic individuals, with a history of atopic dermatitis, adverse food reactions, allergic rhinitis and/or bronchial asthma were studied by Allergy Explorer-ALEX2 macroarray and ImmunoCAP ISAC112 . Lin's concordance correlation coefficient, intraclass correlation coefficient and Bland-Altman plots were used to verify the agreement between continuous values. Cohen's kappa coefficient (k) was assessed for the molecules available in both tests. The degree of relationship was analysed using Spearman's correlation (quantitative variables) and Pearson's χ or Fisher's exact test (categorical variables).

Results: A substantial agreement (κ = 0.795) was observed between the two methods with 94,3% concordant results when results were dichotomized as negative or positive, but if double-negative results were discarded, the agreement dropped to 71%. Conversely, little or no concordance was observed comparing raw data. Considering the 102 molecules shared by both systems, 28/102 (27%) showed an almost perfect agreement (k > 0.81), and concordance was good (k > 0.61) in a further 32 (31%) cases. A perfect to substantial agreement was observed by comparing species-specific aeroallergens. Heterogeneous results emerged comparing panallergens (co-recognition ranging from 30% for tropomyosin/serum albumins to 70% for PR-10/profilin). The correlation among LTP, profilin and PR-10 assayed with ISAC was better than ALEX2 , but the latter identified more positive cases due to the wider number of molecules available. The CCD blocker provided by ALEX test abolishes the carbohydrate determinants signal in 60% of the 33 cases reactive to MUXF3 on the ISAC test.

Conclusion: Despite the excellent concordance of the species-specific markers, the analysis of the panallergens provided in both methods suggests a better performance of the ISAC test on those components, while the ALEX2 test, which includes a larger number of allergens, allowing a broader molecular detection.