The diagnosis of Lipid Transfer Protein allergy -- discriminating between sensitisation and allergy

Background: Lipid Transfer Protein (LTP) is often diagnosed using a combination of clinical history, skin tests and laboratory tests. The peach LTP allergen Pru p 3 is considered a reliable marker of sensitisation to LTP but does not discriminate between allergy and sensitisation alone. Methods: : We retrospectively reviewed the results of adult patients referred for a suspected food allergy to the Allergy Unit at the Royal Brompton & Harefield NHS Foundation Trust (RBHT) London (UK), between 2012-2022 who were sensitised to Pru p 3. Those with a final diagnosis of LTP allergy, were compared to those sensitized to Pru p 3 but not diagnosed with LTP allergy. Results: : Of 285 patients with a positive Pru p 3, 157 (55%) were diagnosed with LTP allergy. LTP allergic patients were more likely to have a higher level of Pru p 3, a lower level of total IgE and a positive skin prick test to peach extract (p<0.001). The ratio of Pru p 3 to total IgE was the most accurate diagnostic marker of LTP allergy in those sensitized to Pru p 3, with a ROC AUC of 0.880. A diagnosis of LTP allergy was significantly associated with sensitisation to the LTP in peanut (Ara h 9, p<0.001), and hazelnut (Cor a 8, p<0.001). Conclusion: Although a range of allergy tests may contribute to the diagnostic workup, the Pru p 3 sIgE:total IgE ratio could be a more effective way of discriminating between sensitization to Pru p 3 and true LTP allergy.