Updated: Feb 25, 2023
Rationale: Up to 30% of the general population develops IgE against cross-reactive carbohydrate determinants (CCDs) found in insect venoms and plants and as a result are at risk of receiving false positive test results from specific IgE (sIgE) immunoassays. ImmunoCAP utilizes a cellulose-based matrix that is known to contain CCD N-glycans that bind to anti-CCD IgE antibodies. This abstract reports on the analysis and resolution of discordant results between NOVEOS and ImmunoCAP in two recent United Kingdom based National External Quality Assessment Service (UK NEQAS) samples.
Methods: UK NEQAS 223-1 and 225-2 sIgE samples were evaluated against NOVEOS and ImmunoCAP neat and spiked with MUXF HSA proglycan CCD blocker (PGB). Sample 223-1 was tested against I001 (honey bee), I003 (yellow jacket), K082 (latex), and W006 (mugwort). Sample 225-2 was tested against F013 (peanut), I001, I003, and W006.
Results: In both samples, CCD blocker caused the majority of ImmunoCAP results to change from positive to negative, while only two near cut-off NOVEOS results changed interpretation. For positive results, CCD blocker caused ImmunoCAP dose values to drop by an average of 2.55 kU/L while NOVEOS values dropped by an average of 0.48 kU/L.
Conclusion: There is a higher risk of false positive results in the ImmunoCAP immunoassay due to non-specific binding to the cellulose solid phase matrix. NOVEOS uses magnetic microparticles and therefore does not have solid phase interference.
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2. Holzweber, F., et al., Inhibition of IgE binding to cross-reactive carbohydrate determinants enhances diagnostic selectivity. Allergy, 2013. 68(10): p. 1269-77.