Identification of potentially tolerated fish species by multiplex IgE testing of a multinational fish-allergic patient cohort

BACKGROUND: Although recent studies indicated that many fish-allergic patients may safely consume certain fish species, no clinical guidelines are available for identification of the exact species tolerated by specific patients.

OBJECTIVE: To investigate whether multiplex IgE testing reveals potentially tolerated fish through absence of IgE to parvalbumin and extracts from specific species.

METHODS: Sera from 263 clinically well-defined fish-allergic patients from Austria, China, Denmark, Luxembourg, Norway and Spain were used in a research version of ALEX2 multiplex IgE quantification assay. Specific IgE to parvalbumins from 10 fish species (9 bony and 1 cartilaginous), and to extracts from 7 species was quantified. IgE-signatures of individual patients and patient groups were analyzed using SPSS and R.

RESULTS: Up to 38% of the patients were negative to cod parvalbumin, the most commonly used molecule in fish allergy diagnosis. 45 patients (17%) tested negative to parvalbumins but positive to the respective fish extracts, underlining the requirement for extracts for accurate diagnosis. Between 60% (Spain) and 90% (Luxembourg) of the patients were negative to parvalbumin and extracts from ray, a cartilaginous fish, indicating its potential tolerance. Up to 21% of the patients were negative to at least one bony fish species. Of the species analyzed, negativity to mackerel emerged as the best predictive marker of negativity to additional bony fish, such as herring and swordfish.

CONCLUSION: Parvalbumins and extracts from multiple fish species relevant for consumption should be used in fish allergy diagnosis, which may help identify potentially tolerated species for individual patients.