• Shelley Dua, James Dowey, Loraine Foley, Sabita Islam, Yvonne King, Pamela Ewan, and Andrew T Clark.
• Department of Medicine, University of Cambridge, Cambridge, UK. Electronic address: shelley.dua@addenbrookes.nhs.uk.
• J Allergy Clin Immunol Pract. 2018 Sep 1; 6 (5): 1692-1698.e1.

BackgroundSerum tryptase is useful in diagnosing drug and venom anaphylaxis. Its utility in food anaphylaxis is unknown.ObjectiveThe objective of this study was to determine whether tryptase rises in food allergic reactions, optimal sampling time points, and a diagnostic cutoff for confirming a clinical reaction.MethodsCharacterized peanut allergic patients were recruited and underwent up to 4 peanut challenges and 1 placebo challenge each. Tryptase was measured serially on challenge days both before (baseline) and during the challenge. The peak percentage tryptase rise (peak/baseline) was related to reaction severity. Receiver operating characteristic (ROC) curves were generated establishing an optimal diagnostic cutoff.ResultsTryptase was analyzed in 160 reactive (9% anaphylaxis) and 45 nonreactive (placebo) challenges in 50 adults aged 18 to 39 years. Tryptase rose above the normal range (11.4 ng/mL) in 4 of 160 reactions. When compared with baseline levels, a rise was observed in 100 of 160 (62.5%) reactions and 0 of 45 placebo challenges. The median rise (95% confidence interval [CI]) for all reactions was 25% (13.3% to 33.3%) and 70.8% (33.3% to 300%) during anaphylaxis. Peak levels occurred at 2 hours and correlated with severity (P < .05). Moderate-to-severe respiratory symptoms, generalized erythema, dizziness, and hypotension were correlated with a higher peak/baseline tryptase (P < .05). ROC curve analysis demonstrated the optimal cutoff to identify a reaction as a 30% rise (sensitivity 0.53; specificity 0.85), area under the curve 0.72 (95% CI, 0.67-0.78).ConclusionsSerum tryptase measurement is valuable in food allergic reactions, and correlates with symptom severity. Comparing peak reaction levels at 2 hours with baseline is essential. A rise in tryptase of 30% is associated with food allergic reactions.Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.

26 keywords...

hide…