Existing Diagnostics

Why Current Methods Are Inadequate

Serum Tryptase

Gold standard. Mast-cell-specific serine protease released during degranulation.

Problems:

• Half-life is short — diagnostic window is 1-2 hours post-reaction
• Useful for confirming acute events, not monitoring
• Elevated baseline suggests mastocytosis (clonal disease) but normal baseline doesn’t rule out MCAS
• Requires blood draw, lab send-out, physician order
• Picogram-range concentrations in circulation — diluted into entire blood volume

Plasma Histamine

• Half-life measured in minutes
• Essentially useless outside immediate reaction confirmation in clinical setting

Urinary 11β-PGF2α

Longer-lived downstream metabolite of PGD2 (mast cell prostaglandin). Renally cleared over hours — integrated signal rather than point-in-time. See 24-Hour Urine Testing for collection details and what’s measured.

Current method: 24-hour urine collection → LC-MS/MS at specialized reference lab (Quest, Mayo Clinic). Patient collects all urine for a day, refrigerates, ships. Not mainstream.

Background noise problem: PGD2 also produced by platelets, airways, brain — not mast-cell-specific. 24-hour collection partially addresses this by averaging over time.

The consumer opportunity: Urinary 11β-PGF2α is the closest thing to a CGM equivalent for mast cell monitoring. Existing chemistry, existing reference range data, just needs miniaturization and consumer packaging. Nobody has built this yet.

Basophil Activation Test (BAT)

Used clinically in Europe more than US. Blood draw, ex vivo challenge of basophils with suspected trigger, measure CD63/CD203c upregulation by flow cytometry.

Why basophils instead of mast cells: Basophils circulate in blood. Mast cells don’t. Practical convenience, not because basophils are better.

Conceptual precedent for the nasal mast cell assay — same logic, wrong cell type.

The Diagnostic Business Problem

Diagnostics are a poor business model — test run once or occasionally vs. drug taken daily. Pharma has weak incentive to develop diagnostics unless paired with a companion drug. Reimbursement infrastructure for complex immunology diagnostics is poor.

Exception: consumer-driven chronic condition monitoring changes the economics entirely. CGM is the model — patients pay out of pocket for longitudinal monitoring. The self-diagnosed chronic illness market (including the “gluten people” population) actively spends money on answers. Some have real mast cell dysfunction; the test doesn’t care.

The Activity-Based Probe Concept

An ingested compound that tryptase cleaves, producing a stable detectable product that accumulates and is renally cleared. Captures tryptase activity rather than tryptase itself, solving the half-life problem.

Oral route specifically targets gut mast cells — most accessible mast cell population via oral dosing, and gut MC activation is primary driver of GI symptoms in MCAS. Not trying to capture systemic tryptase — specifically interrogating gut mast cell activity.

ABP technology exists in research (tryptase-cleavable fluorescent probes), tryptase substrate specificity is well characterized, gut-to-urine pathway is established biology. Nobody has developed this for MCAS diagnostics specifically.

This is genuinely novel territory. Not aware of active development.