Tryptase

Tryptase exists in different isoforms: alpha-tryptase is continuously secreted. Probably the basal serum level of alpha-tryptase reflects the functional state of the total number of mast cells in the body (see below mastocytosis; see below histamine). The beta-tryptase is released during mast cell activation, e.g. during anaphylactic reaction.

Relevance in laboratory diagnostics: Helpful marker to verify an allergic reaction, which may be caused by drugs, insect bites or food. Tryptase may serve as a marker of mast cell activation in allergic rhinitis. Provocation leads to increased tryptase levels in the nasal lavage fluid.

Elevated levels of tryptase after an anaphylactic event can usually be detected 3 to 6 hours after the reaction. The levels normalize within 12-14 hours.

Elevated levels of tryptase >11.4ug/l indicate mastocytosis . At these levels, the risk of an anaphylactic reaction under specific immunotherapy is 2x greater than at 4.25ug/l.

Standard values (may vary depending on the detection system used by different companies): 5.6-13.5 µg/l. Serum should preferably be collected between 15 minutes and 3 hours after the suspicious event that led to mast cell activation. In addition to serum, plasma and nasal fluid are also suitable for analysis. The determination of the basal tryptase concentration is recommended in a guideline of the DGAKI in patients with insect venom allergy in the initial diagnosis.

Method: "Unicap Tryptase" (Pharmacia Diagnostics) measures alpha- and ß-tryptase. Standard values: 5,6-11,4 ug/l. Most patients with elevated basal serum tryptase have mastocytosis.

• The increase in basal serum concentration must be considered a risk factor for life-threatening stinging reactions in patients with insect venom allergy.
• In patients with very severe anaphylactic reactions, elevated tryptase basal levels are found in approximately 30% of patients. This allows the identification of high-risk patients.
• Tryptase determination is useful for questionable reactions with mast cell involvement within the last hours.

1. Przybilla B et al (2004) Insect venom allergy. Guideline of the German Society for Allergology and Clinical Immunology. Allergo J 13: 186-190
2. Renz H et al (2009) In vitro allergy diagnostics. Guideline of the German Society for Allergology and Clinical Immunology (DGAKI). Allergo J 19: 110-128
3. Ruëff F (2003) Increased basal serumtryptase as a risk factor for insect venom allergy. Allergo J 12: 32-38