Inhibition assays are an useful tool to identify the allergen of primary sensitization of cross-reactive allergens. Classical ELISA-based inhibition assays are limited by both the availability of commercial standardized allergen extracts and the experience and knowledge needed for making home-made extracts. Moreover the direct comparison of the inhibition ELISAs outcomes between different laboratories is difficult because of different sources of used allergen extracts and a number of methodological variations. Therefore, we propose a novel ImmunoCap (Phadia, Thermofisher Scientific) based immunoinhibition method with the use of commercially available Caps as the allergen source. The novel ImmunoCap based immunoinhibition method was developed and tested with sera from patients with a well-known cross-reactive sensitization for fig (Ficus carica) and ficus (Ficus benjamina). Results were compared with a classically applied inhibition method, i.e. addition of homemade allergen extract to patient serum. The amount of allergens (fig and ficus extracts) needed to reach a similar degree of inhibition was comparable for both inhibition methods. The ImmunoCap based inhibition assay, in addition to classical inhibition methods, is a valuable tool as the ImmunoCap analyzer and commercial allergens (Caps) are more widely available which makes the outcomes of inhibition tests comparable between different laboratories. Furthermore, in the ImmunoCap inhibition method the same protein source is used for both the inhibition of sIgE and sIgE measurement, which might be even more relevant when multiple cross-reactive allergens are tested.

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Clinical Chemistry and Laboratory Medicine: Associated with FESCC and IFCC
Department of General Practice

Schmidt-Hieltjes, Y. (Yvonne), Teodorowicz, M. (Malgorzata), Jansen, A. (Ad), Den Hartog, G. (Gerco), Elfvering-Berendsen, L. (Lisette), de Jong, N., … Ruinemans-Koerts, J. (Janneke). (2017). An alternative inhibition method for determining cross-reactive allergens. Clinical Chemistry and Laboratory Medicine: Associated with FESCC and IFCC, 55(2), 248–253. doi:10.1515/cclm-2016-0172