Tryptase determination is an indicator for determination of Mastocytosis.(code TRYPTA)
Test method ELISA (EIA) from serum. (blood test)
Persistently elevated levels of tryptase and symptoms of mast cell activation, suggest that a person has mastocytosis. Additional testing is required to confirm this diagnosis.
It is believed that levels of tryptase correspond to the amount of mast cells in people with systemic mastocytosis. Mastocytosis patients have elevated levels of tryptase throughout their lives. The striking thing is that its level has no relation to the patient's level of complaint.
One can have high tryptase levels and experience almost no symptoms. At a value of, say, 15, a whole spectrum of symptoms may already be present.
Mastocytosis is a rare disease with many faces
Mastocytosis is the name for a disease in which there is an increase in abnormal mast cells. Mast cells occur normally in the body and play a role in defense. They are easily recognized in the bone marrow after special staining as deep purple cells that are full of granules. These granules contain a variety of factors, such as histamine or heparin. Some of these substances will cause swelling or redness after stimulation. In an insect sting, for example, mast cells in the skin will keep the poison from spreading too far into the body by causing localized swelling and redness at the site of the sting. The swelling of the nose in hay fever is another example of the action of mast cells found in the nasal mucosa.
A mast cell performs its function and starts to grow when stimulated to do so by certain signals. On the outside of the mast cell is a receptor called KIT (a type of receptor protein) that, after contact with a mast cell growth factor, transmits signals to the inside of the cell. These signals cause the mast cell to secrete substances or grow, for example.
In mastocytosis, an error has occurred in the mast cells. A piece in one place in the KIT receptor has been altered, causing this receptor to mistakenly transmit signals without contact with mast cell growth factors. The mast cell then spontaneously secretes substances or starts to multiply spontaneously, without control.
The disease is first classified into two major groups: mastocytosis, only in the skin, and systemic mastocytosis.
Skin mastocytosis is the most common. Almost always there are brown pigmented patches on the skin, which sometimes itch and swell after contact with heat or when rubbed.
Skin mastocytosis often occurs in children and in the vast majority disappears spontaneously as puberty approaches or even earlier.
Systemic mastocytosis involves an increase in abnormal mast cells in the bone marrow and often in other parts of the body, such as the skin, intestines, liver or spleen.
Classification mastocytosis according to the WHO classification
- Skin Mastocytosis only (most common)
- Indolent systemic mastocytosis (most common)
- Systemic mastocytosis with concomitant other blood disease (rare)
- Aggressive systemic mastocytosis (rare)
- Other forms (mast cell leukemia, mast cell tumors) are very rare.
In mastocytosis patients, the mast cells can cause two types of problems
- The mast cells may be too active
- There may be too many mast cells
The mast cells then take up space in the bone marrow from the normal bone marrow cells, causing a shortage of blood cells that results in anemia and the risk of infections and bleeding.
The liver and spleen may also become swollen due to an increase in mast cells.
No two patients with mastocytosis are the same. There may be hot flashes with a red color, sometimes palpitations and hot flashes, or abdominal pain with diarrhea due to mast cells in the intestine. Patients may experience pain in the muscles and bones, quite often involving severe osteoporosis. This osteoporosis is a result of substances, secreted by the mast cells, which break down the bones. Rare patients have attacks of unwellness, sometimes accompanied by low blood pressure and in extreme cases even loss of consciousness (medical term: anaphylactic shock).
During anaphylactic shock, the level of tryptase usually peaks about 1 to 2 hours after symptoms begin. If a sample is taken too early or too late, the results may be normal. Most patients feel tired and notice that they need more sleep than peers. Stress can sometimes trigger seizures, while a regular life can be protective.
If a patient has symptoms that may indicate skin or systemic mastocytosis, urinalysis is usually done after this blood test to see if there are breakdown products of histamine. Because it is important to know whether a patient has only skin mastocytosis or still has a more extensive, systemic form, bone marrow testing is done in most patients. The sampled bone marrow is then subjected to a number of special tests that are only performed in a few laboratories in the Netherlands. You should therefore ask for a referral through your GP.
Please note this test is not sufficient for diagnosis, and only contributes to a diagnosis:
The diagnosis of systemic mastocytosis is made with 1 major and 1 minor criterion, or - in the absence of a major criterion - with 3 minor criteria.
Two or more infiltrates of mast cells (>15 cells closely spaced) determined in bone marrow biopsies and/or biopsies from other extracutaneous organs using tryptase staining of the mast cells.
Other tests that can be done in case of Mastocytosis:
- >25% of mast cells are spindle-shaped, immature or atypical in biopsy or aspirate of bone marrow or other tissue.
- KIT point mutation at codon 816 in bone marrow or blood or other extracutaneous organs.
Flow cytometry or immunohistochemistry: CD117 (kit receptor) strongly positive cells with co-expression of CD2 and/or CD25.
- Serum tryptase > 20 ng/ml, unless there is an associated clonal myeloid disease (leukemia), because then this criterion is not valid.
- Blood count, chemistry, albumin
- Bone marrow aspirate and biopsy, including flow cytometry, cytogenetics, KIT analysis for D816V mutation.
KIT analysis blood (only if bone marrow KIT analysis is not possible)
- Urine excretion of methylhistamine and methylimidazolacetic acid (MIMA): portion of 2nd fasted morning urine (portion after urinating night urine while sober).
- Echo abdomen or CT abdomen focused on liver/milk/lymph nodes.
- Bone density measurement, skeletal radiographs if necessary.
- On indication other imaging or endoscopy, depending on complaints (stomach/intestine, bones, etc.).
- Consultation with dermatology, in case of suspicious lesion biopsy; documentation urticaria pigmentosa
Do you need to stop medications in advance for a reliable result?
Such as antihistamines (semprex) and/or histamine triggers (e.g., cheese).
Stop medication 24 hours in advance, if possible, after consulting with your practitioner.
The half-life is quite short. Stopping 24 hours in advance appears to be sufficient.
For the exact half-life per medication see: https://www.ntvg.nl/artikelen/antihistaminica-h1-receptorblokkerende-middelen/volledig