Table 2. Consensus criteria of the EU/US group for the diagnosis of mast cell activation syndrome (MCAS).
| Criterion A | Typical clinical signs of severe, recurrent (episodic) systemic MCA are present (often as anaphylaxis) (definition of systemic: involving at least 2 organ systems among cardiovascular, cutaneous, pulmonary and gastrointestinal systems) |
| Criterion B | Involvement of MC is documented by biochemical studies: preferred marker: increase in acute serum tryptase level (ng/mL)(collected 1–4 hours after onset of symptoms) to >(2+1.2*serum baseline tryptase)a |
| Criterion C | Response of symptoms to therapy with MC-stabilizing agents, drugs directed against MC mediator production, or drugs blocking binding of these mediators to their receptorsb |
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MC: mast cells; MCA: mast cell activation.
All 3 MCAS criteria (A+B+C) must be fulfilled to call a condition MCAS.
a
Other MC-derived markers of MCA (histamine and histamine metabolites, PGD2 metabolites, and heparin) have also been proposed, but are less specific as compared to tryptase.
b
Example: histamine receptor blockers.