Mast Cell Tryptase
Investigation of anaphylactic reactions requires 3 serial samples (see collection conditions). Essential feature of an anaphylactic response is the release of vasoactive chemicals from mast cells and circulating basophils. The presence of systemic mast cell degranulation is evidenced by an increase in serum/plasma tryptase. Tryptase, being a large protein has a much longer serum half-life (3 hours) than the histamine (20 min) that is released at the same time.
Suspected analphylactic reaction; Diagnosis of mastocytosis.
It is important that clear records of sample time and date and clinical details are kept. A single tryptase determination is often uniformative. Level at time of peak response must be compared with level after response has receded. A constantly raised tryptase level is characteristic of mastocytosis.
Potassium EDTA Tube or Serum Separator Tube (SST)
Fluorescence enzyme linked immunoassay (Phadia Immunocap 250) using wells coated with anti-tryptase antibody.
As Tryptase values usually return to normal at 24 hours post reaction, three samples (EDTA plasma or serum) are required to be taken up to 1 hour, 3 hours and more than 24 hours of a suspected anaphylatic reaction. When sending samples clearly indicate TIME OF SAMPLE and TIME OF ONSET OF REACTION. The peak response sample, ie sample taken at 1 hour post reaction, should also be tested for C3/C4 levels. A single sample is of less value but it is essential that the time of venepuncture relative to peak anaphylactic response is known.
2 – 14ug/L
Assay range notes
In anaphylaxis the peak plasma concentration can be >200ug/ml. the upper range of detection using this test, but is usually much lower.
5 – 7 days
Immunology, The James Cook University Hospital