This test requires prior approval of a LabPLUS chemical pathologist
Pathologist Approval of Laboratory Tests
Turnaround Time: Between 6 weeks and 8 weeks
The measurement of urine histamine and its metabolite 1-methyl histamine is of diagnostic value in the diagnosis of systemic mastocytosis, diffuse cutaneous mastocytosis, and basophilic leukaemia.
In the above 3 conditions urine 1-MH is extremely high (5-30umoles/24hrs) while urinary histamine may be normal or only slightly raised. Blood histamine and 1-MH may not be raised as histamine is rapidly metabolised and 1-MH is rapidly cleared.
Anaphylaxis:
Histamine measurements are not generally useful in anaphylaxis, because histamine release from mast cells following an immune challenge tends to produce a very short-lived pulse of histamine in blood, which is rapidly metabolised. This may be followed by a refractory period in which histamine turnover is lowered and consequently there is generally little or no increase in 24hr urine histamine or 1-MH. Blood histamine levels increase in the first few minutes but rapidly return to normal, and 1-MH levels are generally unaffected by the challenge.
Serum tryptase is the preferred test for diagnosis of both anaphylaxis and mastocytosis.
Carcinoid tumours:
Gastric and bronchial carcinoid tumours may secrete histamine; however, the best test for carcinoid tumours is urine 5-HIAA (5-hydroxyindoleacetic acid).
Other uses:
Proponents of "orthomolecular medicine" advocate the measurement of urine histamine. This is a form of quackery unsupported by any evidence.
Specimen Transport Instructions for Referring Laboratories:
Patients should be on a histamine-free diet for 24 hours prior to and also for 24 hours during urine collection. Preservatives normally supplied for catecholamine collection should be used. For example: 10-20ml 6M hydrochloric acid added to the specimen container. The referring laboratory should measure the volume of the urine sample and send an aliquot of approximately 30ml together with a signed request form, patient's name, age, address, clinical notes and other details and must include the 24 hour volume measurement. Measurement of the urinary creatinine on 24 hour samples is unnecessary. Collection of random or spot urine collections is not recommended as reference intervals are unknown and the specificity and sensitivity of random urinary histamine and 1-methyl-histamine testing remains uncertain.