Laboratory tests to differentiate mast cell disorders from other disorders

Test	Comment
Plasma-free metanephrine Urinary vanillylmandelic acid	Elevated in pheochromocytoma, not systemic anaphylaxis.
Serum serotonin Urinary 5-hydroxyindoleacetic acid	Elevated in carcinoid syndrome, not systemic anaphylaxis.
Serum vasointestinal polypeptide hormone panel: Pancreastatin, vasoactive intestinal peptide, substance P, neurokinin	To rule out gastrointestinal tumors or medullary carcinoma of the thyroid, which can secrete these vasoactive mediators.
Plasma kallikrein High molecular weight kininogen	To assess activation of the contact pathway, leading to production of bradykinin.
Plasma C3a or C5a	To assess activation of the complement pathway, leading to production of these anaphylatoxins.

C3a: complement component 3a; C5a: complement component 5a.

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