The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, part 8
I have answered the 107 questions I have been asked most in the last four years. No jargon. No terminology. Just answers.
14. Are there any special instructions for the tests to diagnose mast cell disease?
• There are a lot of tests used to diagnose mast cell disease. There are certainly people who slip through the cracks with the current diagnostic criteria.
• Remember this as you read the following: DO NOT, UNDER ANY CIRCUMSTANCES, EVER, DISCONTINUE MEDICATION FOR TESTING WITHOUT EXPLICIT INSTRUCTIONS TO DO FROM A DOCTOR THAT UNDERSTANDS MAST CELL DISEASE. Stopping medications for mast cell disease can be very dangerous.
• The biopsy forms the centerpiece of diagnosis of both cutaneous and systemic forms of mastocytosis.
• You can increase your chance of positive skin biopsy by choosing either a permanent lesion or an area of skin that is frequently reactive.
• For internal organs, including bone marrow, you can’t always tell where to biopsy just by looking. The area may look normal but show inflammation when viewed with a microscope.
• If patients do not need to take daily corticosteroids because they do not make their own (adrenal insufficiency or Addison’s disease), they are often recommended to not use corticosteroids (prednisone or similar) for five days before a bone marrow biopsy. Taking corticosteroids can tell your body to make a lot of extra white blood cells which can make it harder to give a correct diagnosis.
• The CKIT D816V mutation test is often done on a blood sample. It is much more accurate when a bone marrow biopsy is tested because there are many more mast cells. Mast cells do not live in the blood so the blood test is less accurate. If the test is positive in blood, we assume that the patient is truly positive. If the test is negative in blood, we are not sure if the patient is truly negative.
• Serum tryptase is a test with a lot of caveats. It is influenced heavily by timing and patient factors like weight. Many people with mast cell disease have normal serum tryptase. It is good for tracking progression of disease in patients with systemic mastocytosis.
• About 85% of patients with systemic mastocytosis have a baseline tryptase value over 20 ng/mL. Patients with monoclonal mast cell activation syndrome may also have baseline tryptase value over 20 ng/mL. For these patients, they should have two different tests from days when they are not especially reactive, or have had anaphylaxis.
• For patients with mast cell activation syndrome, we are often looking for an increase in tryptase during a reaction or anaphylactic event. In these patients, experts recommend having blood drawn 15 minutes to 4 hours after onset of the event.
• Another sample should be drawn 1-2 days later so that you have a sample to compare with the tryptase level during the event. Many experts accept a level increased by 20% plus 2 ng/mL above the baseline to be indicative of mast cell activation. (I made a typo on this that said 20% to 2 – sorry!)
• As we have previously discussed, many mast cell mediators should be kept cold because they break down quickly. 24 hour urines for n-methylhistamine, prostaglandin D2, 9a,11b prostaglandin F2, and leukotriene E4 should be kept cold.
• Performing a 24 hour urine when you are having a reaction event can increase the likelihood of mediator release.
• COX inhibitors will interfere with prostaglandin production. Some patients stop these meds before giving 24 hour urines for prostaglandin testing. DO NOT STOP MEDS WITHOUT BEING ADVISED BY AN EXPERIENCED MAST CELL PROVIDER.
• Lipoxygenase inhibitors will interfere with leukotriene production. Some patients stop these meds before giving 24 hour urines for leukotriene testing. DO NOT STOP MEDS WITHOUT BEING ADVISED BY AN EXPERIENCED MAST CELL PROVIDER.
• Heparin is very heat sensitive. Plasma heparin must be kept cold. One study reported that a tourniquet on the upper arm for ten minutes before drawing the sample increased the change of detecting mast cell activation with this test.
• Chromogranin A is influenced by many other conditions and medications. It is important that those other conditions be ruled out. This may require lengthy body scans and other tests. Chromogranin A is influenced by proton pump inhibitors, meds that are commonly taken by mast cell patients. DO NOT STOP MEDS WITHOUT BEING ADVISED BY AN EXPERIENCED MAST CELL PROVIDER.
For more detailed reading, please visit these posts:
The Provider Primer Series: Mediator testing
Patient questions: Everything you wanted to know about tryptase
The Provider Primer Series: Mast cell activation syndrome (MCAS)
The Provider Primer Series: Cutaneous Mastocytosis/ Mastocytosis in the Skin
The Provider Primer Series: Diagnosis and natural history of systemic mastocytosis (ISM, SSM, ASM)
The Provider Primer Series: Diagnosis and natural history of systemic mastocytosis (SM-AHD, MCL, MCS)