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Licensed Unlicensed Requires Authentication Published by De Gruyter April 27, 2022

A comprehensive comparison between ISAC and ALEX2 multiplex test systems

  • Anouk C.M. Platteel , Pieter van der Pol , Jean-Luc Murk , Ingrid Verbrugge-Bakker , Marian Hack-Steemers , Theo H.W.M. Roovers and Michiel Heron ORCID logo EMAIL logo



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 ALEX (Allergy Explorer, ALEX2 test introduced on the market November 2019) multiplex platform and to compare it with the ImmunoCAP ISAC® test system.


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.


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.


The method comparison between ISAC and ALEX2 multiplex tests showed a high concordance for those allergen components present on both platforms.

Corresponding author: Michiel Heron, Medical Microbiology and Immunology, Diakonessenhuis, Bosboomstraat 1, Utrecht, Netherlands, E-mail:

  1. Research funding: None declared.

  2. Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.

  3. Competing interests: Authors state no conflict of interest.

  4. Informed consent: Informed consent was obtained from all individuals included in this study.

  5. Ethical approval: The local Institutional Review Board deemed the study exempt from review.


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Supplementary Material

The online version of this article offers supplementary material (

Received: 2022-02-28
Accepted: 2022-04-04
Published Online: 2022-04-27
Published in Print: 2022-06-27

© 2022 Walter de Gruyter GmbH, Berlin/Boston

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