Background: The basophil activation test (BAT) has high accuracy to diagnose peanut allergy (PA) and can reduce the need for oral food challenges (OFC); however, so far it has not been incorporated in clinical practice. Methods: We compared two BAT methodologies, their performance in two separate laboratories, their diagnostic utility and impact of BAT in clinical-decision-making in a specialised centre. Results: 102 children being assessed for PA were tested on BAT (72 allergic, 30 sensitised tolerant). There was little internal variation (CV<15%) and a very strong correlation (Rs>0.95) between BAT performed across laboratories. The 2 BAT methods were correlated but not interchangeable and 19% of cases had opposite results. The in-house BAT method (IH-BAT) was superior, as demonstrated by its better diagnostic performance (area under the ROC curve 0.929/0.957 versus 0.892/0.895 for CD63/CD203c), lower number of non-responders (4% versus 14%), lower background basophil activation (4% versus 9%) and less need for oral food challenges (29/12 versus 37/20 for OFC/positive OFC). BAT was feasible and well-accepted by clinicians: no patient with positive BAT was referred for OFC; only 37% of all tested patients needed an OFC and 14% of these (5% of total) reacted during OFC, which corresponded to 72/89% decrease in OFC/positive OFC, respectively, with the integration of BAT in the diagnostic work-up for peanut allergy. Conclusions: The BAT is a robust test that can reliably be transferred between laboratories; however, different BAT methods are not interchangeable. BAT was well integrated in the clinical decision-making process in a specialised centre.

Background: Various biomarkers are used to define peanut allergy (PA). We aimed to observe changes in PA resolution and persistence over time comparing biomarkers in PA and peanut sensitised but tolerant (PS) children in a population-based cohort. Methods: Participants were recruited from the EAT and EAT-On studies, conducted across England and Wales and were generally well exclusively breastfed babies recruited at 3 months old and followed up until 11 years old. Clinical characteristics, skin prick test (SPT), sIgE to peanut and peanut components and mast cell activation tests (MAT) were assessed at 12m, 36m and 7-11y. Results: The prevalence of PA was 2.1% with only 1 child having PA resolution at 7-11y. PA children had larger SPT size, higher peanut-sIgE, Ara h 2-sIgE and MAT (all p<0.001) compared to PS children at 36m and 7-11y. SPT, peanut-sIgE, Ara h 2-sIgE and MAT between children with persistent PA, new PA, outgrown PA and PS were statistically significant at both 36m and 7-11y (p<0.001). Those with persistent PA had SPT, peanut-sIgE and Ara h 2-sIgE that increased over time and MAT which was highest at 36m. New PA children had increased SPT and peanut-sIgE from 36m to 7-11y, but MAT remained low. PS children had low biomarkers across time. Conclusions: In this cohort, few children outgrow or develop new PA between 36m and 7-11y. Children with PA have significantly higher SPT, peanut-sIgE, Ara h 2-sIgE and MAT compared to PS children, evident from 12-36m of age.

We report for the first time the case of allergy to egusi seeds in an atopic child of Nigerian origin with allergy to other seeds and nuts. This case highlights the need to know and explore less common foods as potential allergens, the importance of modified skin prick testing and the basophil activation test to support the diagnosis of rare food allergies and of awareness about world cuisine and exotic foods as potential allergens.