A comprehensive comparison between ISAC and ALEX2 multiplex test systems

Abstract Objectives Diagnosis of type I hypersensitivity is based on anamnesis, provocation as well as blood- and skin testing. Multiplex specific IgE (sIgE) testing enables determination of sIgE antibodies against multiple recombinant or purified natural allergen components. The aim of this study was to evaluate the performance of the novel ALEX2® (Allergy Explorer, ALEX2 test introduced on the market November 2019) multiplex platform and to compare it with the ImmunoCAP ISAC® test system. Methods Serum samples of 49 patients, routinely determined with ISAC, were selected based on positive results covering in total most of the 112 ISAC components. Cohen’s kappa, negative percent agreement (NPA), and positive percent agreement (PPA) of ALEX2 data compared to ISAC data (as a non-reference standard) were computed for those allergen components present on both platforms (n=103). Furthermore, in some samples sIgE results against allergen extracts and/or -components tested with either ImmunoCAP® (ThermoFisher) or IMMULITE® (Siemens) were available and compared to ALEX2 results. Results The overall agreement between ISAC and ALEX2 common allergen components was 94%. NPA and PPA were respectively 95 and 90%. Kappa values differed for specific allergen groups and varied between 0.60 and 0.92 showing moderate to almost perfect agreement. Of the qualitative discrepancies between ALEX2 and ISAC, 59% were related to weak positive results i.e. results under 1 kUA/L or 1 ISU, respectively. Conclusions The method comparison between ISAC and ALEX2 multiplex tests showed a high concordance for those allergen components present on both platforms.