D1.70 - No more restrictive diets for LTP allergic patients. The importance of oral food challenge

The diagnosis and management of patients allergic to lipid transfer proteins (LTP) is very complex since skin prick test (SPT) and determination of sIgE often do not differentiate between sensitization and allergy to LTP, being the oral food challenge (OFC) the gold standard to confirm the diagnosis. We performed a descriptive analysis of patients diagnosed with LTP allergy in our unit and their results in oral challenge with plant-foods.

We selected patients diagnosed with allergy to peach LTP (Pru p 3), with skin prick test (SPT) positivity (papule >3mm2) and/or specific IgE (sIgE >0.35 kUA/L) by ImmunoCAP system. Skin tests were performed with peach extract enriched with Pru p 3 and a battery of plant-foods including wheat, corn, peanut, hazelnut, walnut, almond, lettuce, tomato, apple and kiwi. sIgE was analyzed using the ALEX multiplex analysis platform. Several food challenges were performed in patients with avoidance diets.

25 patients (52% women) with a mean age of 29 years were included. 15 patients (60%) had reactions with peach, 15 patients (60%) with other fruits, 21 patients (84%) had reactions with nuts and 10 patients (40%) with other plant-foods. 32% of patients presented grade 1 reactions (OFASS-5 classification), 48% grade 2, 8% grade 3 and 12% grade 4.

The mean number of plant-foods inducing reactions was 5.56, and the mean number of plant-food positives in the SPT battery was 6.44. However, in the ALEX the mean number of LTP plant-food positives was 5.04. Three patients had none LTP plant-food positives, two of them recognized other plant food-allergens (profilin and PR-10) and the other had only positive the Pru p 3 SPT.

We performed a total of 39 OFC in 14 patients, 22 with nuts, 6 with peanut and the rest with other plant-foods, different from peach. 31 OFC (79%) were negative. In 5 OFC (peanut and nuts), patients reported oropharyngeal symptoms that resolved spontaneously, completing the challenge. One patient had a late reaction to peanut consisting of abdominal pain, diarrhea, and vomiting that did not require treatment. Another patient had oropharyngeal symptoms, palpebral edema and generalized pruritus with peanut and oropharyngeal symptoms and generalized urticaria with walnut that required treatment.

OFC is essential in patients allergic to LTP, as they often follow very restrictive diets. In our study, we have seen that it is a safe procedure that allows the introduction of foods that are avoided, only with mild systemic reactions.