Characteristics of Tree Nut Challenges in Tree Nut Allergic and Tree Nut Sensitized Individuals
Sunday, March 6, 2016
South Exhibit Hall H (Convention Center)
Christopher E. Couch, MD, Timothy J. Franxman, MD, Matthew J. Greenhawt, MD MBA MSc
Rationale: Characteristics and outcomes of tree nut (TN) oral food challenges (OFC) in patients with TN allergy or sensitization alone are poorly studied. 

Methods: Open TN OFCs performed between 2007-2015 at a food allergy referral center were analyzed for outcome, skin prick test (SPT) wheal size, food-specific IgE (sIgE), peanut co-allergy, and TN sensitization versus clinical allergy.  Delayed OFC was defined as >12 months from time of sIgE <2 kUA/L.

Results: Overall passage rate was 86% in 159 TN OFC in 102 patients (47 almond, 28 walnut, 27 cashew, 18 hazelnut, 14 pecan, 13 pistachio, and 2 Brazil nut).  Passage rate was 76% (n=67) in patients with a history of a prior TN reaction, and 92% (n=59) among those with TN sensitization only (mean sIgE=1.24 kUA/L; range 0.35-9.13).  Passage rate was 89% (n=118/134) if TN-sIgE <2 kUA/L, and 69% (16/23) if TN-sIgE ≥2 kUA/L.  Among n=54 peanut allergic patients with tree nut co-sensitization (e.g., no TN reaction history), TN OFC passage rate was 96%. In 40 TN OFCs with TN SPT wheal size ≥3 mm, 63% passed, with mean wheal 4.8 mm [range 3-11] among those passing vs. 7.9 mm (range 3-20) in those failing.  TN OFC was delayed in 60% (89/149), and mean time to OFC was 50 months (range 14-108).

Conclusions:  TN challenges are frequently passed in patients with both TN sensitization or TN reactivity, despite TN PST>3mm or TN-sIgE >2 kUA/L.  However, OFC is frequently delayed in patients with TN-sIgE<2KUA/L.  Nearly all peanut allergic patients with TN co-sensitization passed TN challenge.