At a glance
Also known as
Mast cell tryptase; Alpha tryptase; Beta tryptase; Mature tryptase
Why get tested?
To help diagnose the cause of , mastocytosis, or activation
When to get tested?
When you have symptoms such as flushing, nausea, throat swelling or low blood pressure that may be due to a life-threatening allergic reaction; when your doctor suspects that you have mastocytosis or mast cell activation; when you are considering insect venom immunotherapy.
A blood sample drawn from a vein in your arm.
Test preparation needed?
None, but timing of the sample soon after the beginning of symptoms can be important.
What is being tested?
This test measures the amount of tryptase in the blood. Tryptase is an that is released, along with histamine and other chemicals, from when they are activated, often as part of an allergic immune response.
Mast cells are large tissue cells found throughout the body, but in highest amounts in the skin, in the lining of the intestine and air passages, and also in the . Mast cells are part of the body's normal response to injury as well as allergic (hypersensitivity) responses. They contain granules that store a number of chemicals, including tryptase and histamine, that are released when mast cells become activated. In the body, mast cells recognise and bind , a special type of that is often increased in people with allergies and infections. When that is bound to the surface of mast cells attaches to its target (), mast cells become activated and release their contents. The chemicals released from mast cells (especially histamine) are responsible for many of the symptoms in persons with allergies.
Mast cells contain different forms of the enzyme tryptase, termed alpha (α) and beta (β) tryptase, in both inactive (protryptase) and active forms. In the body, beta tryptase is typically the predominant form of mature tryptase. Testing can be performed to measure total tryptase, which is all of the forms together, or mature tryptase, which measures the mature forms of alpha and beta tryptase. Comparison of the results of these two tests in a total-to-mature ratio may be useful in some instances though is not available at present in Australia.
Normally concentrations of tryptase in the blood are very low. When mast cells are activated, levels increase rapidly, rising within 15 to 30 minutes, peaking at 1 to 2 hours, and returning to normal after several hours to a couple of days. In persons with severe allergies, activation of many mast cells can cause a severe form of allergic reaction termed anaphylaxis, which can cause low blood pressure, hives (blisters on the skin), severe narrowing of the air passages, and even death. Tryptase levels will be very high in persons with only if they have had low blood pressure with the reaction. In many food associated reactions, tryptase may not be elevated.
In some cases, tryptase levels will be high in persons with mast cell activation disorders, in which mast cells become activated without apparent allergies or other reasons.
Tryptase levels can also be significantly and persistently increased with mastocytosis, a rare group of disorders associated with the neoplastic proliferation of mast cells and their infiltration and accumulation in the skin (cutaneous mastocytosis) and/or in organs throughout the body (systemic mastocytosis). Systemic mastocytosis may progress slowly and be relatively slowly progressive or may be aggressive, causing organ dysfunction and, in rare cases, is a form of leukaemia. It may also be associated with some forms of lymphoma.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed, but timing of the sample soon after the beginning of symptoms can be important. Talk to your doctor about the best time to draw your sample.