Can tryptase levels be useful in the diagnosis of anaphylaxis?

Published Online: October 15, 2015

The diagnosis of anaphylaxis currently relies on a suggestive clinical history after exposure to a potential triggering agent. However, the diagnosis may be challenging because it is not always possible to identify a clear trigger and its presentation may mimic that of other serious medical conditions. In addition, there are currently no reliable diagnostic biomarkers available to confirm the diagnosis. Although elevated tryptase levels during anaphylaxis were suggested to support the diagnosis of anaphylaxis, there are no large-scale studies establishing its diagnostic properties.

In an article recently published in The Journal of Allergy and Clinical Immunology (JACI), De Schryver and colleagues evaluated tryptase levels and predictors of elevated tryptase levels in children presenting with anaphylaxis (defined as > 11.4 µg/L during reaction and for those with a post-reaction level, defined as a reaction level of at least 2 ng/mL + [1.2 x post-reaction tryptase level]). Data were collected on symptoms, triggers, and management of anaphylaxis over 4 years from 203 children presenting with anaphylaxis to the Emergency Department of the Montreal Children’s Hospital. Tryptase levels were assessed within the first 2 hours of a reaction and in a subset of children, they were also assessed at baseline (at least 24 hours post-reaction). The authors also evaluated the association between elevated tryptase levels and risk factors such as age, sex, reaction trigger, severity of reaction, presence of atopy, and the time interval between tryptase measurements.

The authors found elevated tryptase levels in only 20% of the children with anaphylaxis and only severe reactions were associated with tryptase levels of 11.4 µg/L or more. However, tryptase levels exceeding the threshold level of 2 ng/ml + 1.2 x (baseline tryptase level) were observed in 53% of children and in 85% of those with severe reactions.  In all children experiencing a severe reaction who had tryptase measured within 2 months of the reaction, the level exceeded this threshold

The author’s findings suggest that the usefulness of tryptase levels improves when reaction levels are compared to post-reaction levels drawn within 2 months of the reaction.

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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