Comparison of cross-reactive carbohydrate determinant reactivity using recombinant component resolve

J. Dodds ; A. Cruz-Campos ; B. Braddock; E. Laderman Hycor Biomedical Inc, United States of America

Beth Laderman, Ph.D., CSO from HYCOR Biomedical presented at ISMA Flash session hosted by EAACI, about why it's more beneficial not to use a cellulose-based solid phase in allergy testing.

Background

Up to 30% of the general population develops IgE against cross-reactive carbohydrate determinants (CCDs) and are at risk of receiving false positive test results from specific IgE (sIgE) immunoassays. To mitigate the risk of CCD reactivity, component resolved diagnosis (CRD) using recombinant allergens was proposed in place of whole extracts which contain naturally occurring CCD structures. However, previous studies have reported falsely elevated results when employing CRD on diagnostic assays with a cellulose-based matrix. This study aims to compare the relative effectiveness of recombinant components in reducing the prevalence of false positives on a non-cellulose and cellulose-based in vitro sIgE automated platform.

Method

5 recombinant components were used for the comparison, peach (rPru p 3), peanut (rAra h 2), hazelnut (rCor a 1 PR-10), and birch (rBet v 1, rBet v 2)

A total of 500 retrospective results from de-identified, remaindered samples were examined to identify discordant data between NOVEOS® and predicate devices. 45 samples were suspected to have anti-CCD IgE, but due to availability, only 37 samples were incubated with MUXF-HSA proglycan CCD-blocker (PGB) and tested on NOVEOS against peach (rPru p 3), peanut (rAra h 2), hazelnut (rCor a 1 PR-10), and birch (rBet v 1, rBet v 2) non-glycosylated recombinant components. To detect CCD reactivity, two mixes with known CCDs were tested in tandem with the recombinant components. 15 of the 37 serum samples demonstrated CCD IgE reactivity against the two mixes on NOVEOS and were then tested with and without PGB on ImmunoCAP for comparison.

Method Comparison of NOVEOS vs. ImmunoCAP represented for each component allergen

Results

8 of the 15 samples produced false positive results when tested against the 5 recombinant components on ImmunoCAP and no false positives were detected when these samples were tested on NOVEOS. Out of the 40 total results (8 samples x 5 recombinant components), 31 results (77.5%) changed in interpretation from positive to negative on ImmunoCAP in the presence of PGB when using 0.35 kU/L as the cutoff.

Comparison of NOVEOS and ImmunoCAP data for the major peanut allergen, Ara h 2, in the 8 samples exhibiting CCD reactivity

Conclusion

The recommendation to utilize CRD when testing on sIgE assays was a potential remedy for the frequent occurrence of false positive results caused by extract-based testing. Despite using recombinant allergens free of CCDs, the risk of false positive sIgE results remains when tested on ImmunoCAP due to the cellulose solid phase matrix which possesses glycoproteins. However, the prevalence of false positive results stemming from CCD interference was completely mitigated when testing with recombinant components on NOVEOS due to the absence of the cellulose matrix.

Breakdown of the 31 total false positive (FP) results on ImmunoCAP among the 5 recombinant allergens in 8 samples

References:

1. Altmann F. Coping with cross-reactive carbohydrate determinants in allergy diagnosis. Allergo J Int. 2016;25(4):98-105. DOI: 10.1007/s40629-016-0115-3. Epub 2016 Jun 25. PMID: 27656353; PMCID: PMC5016538. https://pubmed.ncbi.nlm.nih.gov/27656353/

2. Treudler R, Simon JC. Overview of component resolved diagnostics. Curr Allergy Asthma Rep. 2013 Feb;13(1):110-7. doi: 10.1007/s11882-012-0318-8. PMID: 23076421. https://pubmed.ncbi.nlm.nih.gov/23076421/