Tryptase Levels in Anaphylaxis Diagnosis

Understanding Tryptase in Anaphylaxis

Tryptase is an enzyme primarily released by mast cells during degranulation, with two main forms: α-tryptase and β-tryptase, where β-tryptase is the form specifically released during anaphylactic reactions 1, 2

Serum tryptase levels peak approximately 1-1.5 hours after onset of anaphylaxis, with levels persisting for up to 5 hours after symptom onset, and the optimal time to measure serum tryptase is between 1-2 hours but no longer than 6 hours after symptom onset 3, 4
Tryptase has a half-life of approximately 2 hours in circulation, causing levels to fall rapidly following an anaphylactic reaction 1

The change in tryptase concentration is more helpful than absolute values for diagnosing anaphylaxis, with a rise of at least 20% + 2 μg/L from baseline being diagnostic 1
Intravenous fluid administration during treatment can dilute blood and lower measured tryptase concentration, and anaphylaxis can occur through pathways that don't cause tryptase elevation 1
A normal tryptase level does not rule out anaphylaxis, and the current tryptase assay has high specificity but relatively low sensitivity 1

For postmortem diagnosis, tryptase levels may be helpful but have lower predictive value than samples taken during life 1