Résumé
Background: Multi-allergen respiratory screening tests aim to detect specific serum IgE antibodies to common airborne allergens. The methodological range has recently expanded, but the comparative performance of the available tests is not known. Our objective was to evaluate the technical performance of three commonly used multi-allergen tests: SX01™ (Hycor®, Los Angeles, USA), Phadiatop™ (Thermo Fisher Scientific®, Uppsala, Sweden) and Alatop™ (Siemens® Healthcare GmbH, Erlangen, Germany).Method: Retrospective analysis by SX01 and Alatop of 113 con- secutive serum samples tested with Phadiatop™ (2019–2021, Synlab Provence, median age 18 years, range 2–78, sex ratio 1). Results were expressed as positive or negative according to the manufacturer's threshold (Phadiatop 0.35 kUA/L, SX01 0.17 kUA/L and Alatop index >0.9). The Phadiatop and Alatop tests comprise extracts of common airborne allergens (house dust mites, cat, dog, tree, grass and weed pollen, airborne moulds), as opposed to the SX01 test which is a mix of major and marker molecular allergens from house dust mites (Der p 1, Der p 2), cat (Fel d 1), dog (Can f 1, Can f 2, Can f 5), grass (Phl p 1) and tree (Bet v 1) pollen as well as the highly cross-reactive dog serum albumin Can f 3. Clinical data were collected for discordant cases.Results: Positive results were found in 46% with Phadiatop, in 38% with SX01, and 40% with Alatop (Table). The interassay agreement for the 3 methods was 86% (97/113), i.e. 93% of negative results (57/61) and 75% of positive (39/52) results taking the Phadiatop results as a reference. Discordant results were predominantly positive with Phadiatop and negative with SX01 or Alatop, and associated with clinical history of allergic rhinitis. In two patients, isolated positive Alatop results were observed without a clinical history of allergic symptoms.Conclusion: Despite differences in their composition, there was very good overall concordance of the three screening assays, remarkably for negative tests. The absence of fungal, insect, and some major grass allergens could explain the lower sensitivity of SX01 in our study. Conversely, biotin interference could be involved in isolated positive results with the Alatop mix