Serum Tryptase

Aka: Serum Tryptase, Tryptase

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II. Indications

  1. Anaphylaxis confirmation in unclear cases
    1. Levels rise 30 minutes after onset and peak at 1-2 hours of Anaphylaxis
    2. Serum Tryptase is often normal in food-related reactions
  2. Mastocytosis (Clonal Mast Cell disease)

III. Physiology

  1. Tryptase is a marker of systemic Mast Cell degranulation
  2. Tryptases are a family of neutral Serine proteases, enzymes with activity similar to trypsin
    1. Tryptases cleave Protein substrates after Arginine or Lysine residues
  3. Tryptases are primarily found in the secretory granules of Mast Cells
    1. Tryptases are released during Mast Cell degranulation (e.g. Anaphylaxis)

IV. Causes

  1. Episodic Serum Tryptase increase
    1. Anaphylaxis
    2. Hymenoptera Venom Anaphylaxis
  2. Persistent Serum Tryptase increase (>8 ng/ml)
    1. Mastocytosis
    2. Hereditary Alpha-Tryptasemia
  3. Other Causes of Elevated Serum Tryptase
    1. Acute Myelocytic Leukemia
    2. Myelodysplastic Syndrome
    3. Hypereosinophilic Syndrome (FLP1L1-PDGFRA mutation)
    4. End Stage Renal Disease

V. Labs

  1. Anaphylaxis
    1. Obtain level on presentation, within 1-2 hours, and again in 24 hours after presentation
    2. Levels consistent with systemic Mast Cell activation in Anaphylaxis
      1. Serum Tryptase>11.4 ng/ml OR
      2. Serum Tryptase increase over baseline of 20% PLUS 2 ng/ml
  2. Mastocytosis
    1. Serum Tryptase >20 ng/ml (systemic mastocytocytosis)

VI. References

  1. Bakerman (2014) ABCs of Interpretive Laboratory Data, p. 544
  2. Golden (2024) Ann Allergy Asthma Immunol 132(2): 124-76 +PMID: 38108678 [PubMed]

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