You have the flushing, the hives, the food reactions, and the racing heart. Someone finally mentioned mast cell activation syndrome and ordered a tryptase test. It came back normal, and the conversation ended there.
A normal tryptase is one of the most common reasons MCAS gets dismissed. Here’s why it isn’t the final word.
What tryptase measures
Tryptase is an enzyme stored in mast cells and released when they activate. There are two ways it gets measured:
- Baseline tryptase reflects how many mast cells you have and your genetic makeup. It’s typically drawn when you feel well.
- Event tryptase is drawn during or shortly after a flare, to capture a spike.
Why a normal baseline doesn’t rule out MCAS
Most people with MCAS have a normal baseline tryptase. An elevated baseline points toward other possibilities, including:
- systemic mastocytosis, a condition with increased numbers of mast cells, which is considered when baseline tryptase is well above normal, and
- hereditary alpha-tryptasemia, a common genetic trait (Lyons et al., Nature Genetics, 2016) that raises baseline tryptase and has been associated with flushing, GI symptoms, and dysautonomia in some people.
MCAS is about mast cells overreacting, not about having too many. So the baseline is often unremarkable.
Timing matters more than most people are told
The international consensus criteria (Valent et al., 2012) describe a meaningful rise as an increase of 20% plus 2 ng/mL above your own baseline, measured within roughly one to four hours of symptom onset.
That means:
- A single tryptase drawn on a good day can’t show a rise.
- A result can sit within the lab’s “normal” range and still represent a significant rise for you.
- Comparing an event level with your own baseline tells you far more than either number alone.
Tryptase isn’t the only mediator
Mast cells release many chemicals, and not every flare raises tryptase. Other markers sometimes measured include:
- N-methylhistamine, a breakdown product of histamine, measured in urine
- Prostaglandin D2 metabolites, such as 2,3-dinor-11β-PGF2α
- Leukotriene E4
These tests have their own challenges. Timing, collection method, and sample handling, including keeping samples cold, can all affect results. Our lab testing page explains what we use and what each test measures.
What a careful evaluation looks like
- A detailed flare history: what triggers episodes, which body systems are involved, and how long they last.
- A plan for timed testing: so a sample can be collected during a real flare, not just on a calm day.
- Your own baseline: for comparison.
- Ruling out other causes: true IgE allergy, alpha-gal syndrome, celiac disease, and other conditions that mimic mast cell symptoms.
When to get emergency care
Call 911 for:
- throat swelling,
- trouble breathing,
- widespread hives with dizziness, or
- fainting.
Use a prescribed epinephrine auto-injector as directed.
Serving Oklahoma City, Tulsa, and all of Oklahoma
Venturis Clinic sees patients from Oklahoma City and surrounding areas, including Tulsa, and from across Oklahoma. Learn more on our MCAS in Oklahoma City page.
Frequently asked questions
Can you have MCAS with normal tryptase? Yes. Baseline tryptase is usually normal in MCAS. A rise during a flare compared with your own baseline is more informative.
When should tryptase be drawn? Event tryptase is most useful within about one to four hours of a flare starting, and should be compared with a baseline drawn when you’re well.
What does high baseline tryptase mean? It can point to hereditary alpha-tryptasemia or, less commonly, mastocytosis, and should be evaluated further.
Are urine tests better than tryptase? They measure different mediators and can add information, but they have their own collection and timing challenges.
Told your labs rule it out? Book a free 15-minute discovery call, or learn more about MCAS care in Oklahoma City.
This page is for educational purposes and is not a substitute for individual evaluation.
By Alvin Philipose, DC, ICCP
Sources
- Valent P, et al. Definitions, criteria and global classification of mast cell disorders with special reference to mast cell activation syndromes: a consensus proposal. International Archives of Allergy and Immunology. 2012;157(3):215–225.
- Lyons JJ, et al. Elevated basal serum tryptase identifies a multisystem disorder associated with increased TPSAB1 copy number. Nature Genetics. 2016;48(12):1564–1569.