Multiplex IgE reactivity without a documented corresponding phenotype: cross-sectional patterns and routine-care...

Background. Multiplex diagnostics may identify IgE reactivity without a corresponding phenotype documented at testing. This record-level discordance can reflect incomplete history, limited exposure, cross-recognition, or broader atopy and is not equivalent to asymptomatic sensitization. We described concordance across six allergen groups and routine-care reassessment of selected Pru p 3/nsLTP and Hymenoptera findings. Methods. We retrospectively analyzed ALEX2 assessments, retaining one index-positive test per patient and allergen group. Pairs were classified according to whether a compatible phenotype was documented at index assessment. Follow-up of selected Pru p 3/nsLTP and Hymenoptera findings were non-standardized, descriptive, and restricted to patients retained in routine care by July 2026. Results. Among 3,636 patients, 1,241 were positive to at least one group, yielding 1,698 pairs: 667 (39.3%) had a documented corresponding phenotype and 1,031 (60.7%) did not. Atopic dermatitis did not increase record-level discordance compared with respiratory atopy without atopic dermatitis. Among 316 Pru p 3-positive patients without a documented phenotype, 290 were retained; 219 reported a compatible post-index reaction after plant-food exposure and 71 did not, including 55 with documented tolerance. Among 204 Hymenoptera-reactive patients without a documented sting phenotype, 112 were retained; 31 reported a post-index sting-associated event and 81 reported no post-index sting. Conclusions. In this tertiary-care cohort, absence of a documented corresponding phenotype was frequent. Routine-care reassessment yielded heterogeneous exposure-based outcomes but cannot estimate asymptomatic sensitisation, clinical penetrance, or future risk. The findings support clinical verification rather than automatic dismissal or allergy labelling.