Specimen Requirements

Minimum Specimen Requirements

Stability

Days Performed

Tue, Thu

Turnaround Time

4 - 8 days

Methodology

Reference Range

Special Info

Patient must not be taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine as these medications increase N-methylhistamine (NMH) levels. Collect the random urine specimen within a few hours of onset of symptoms.

Clinical Info

Useful for screening and monitoring mastocytosis and disorders of systemic mast-cell activation, such as anaphylaxis and other forms of severe systemic allergic reactions using random urine specimens. Monitoring therapeutic progress in conditions that are associated with secondary, localized, low-grade persistent, mast-cell proliferation and activation such as interstitial cystitis. Patients with chronic mast cell activation often have chronically elevated N-methylhistamine (NMH) levels and will sometimes have intermittent NMH elevations. In these cases, a 24-hour urine collection is preferred [see N-Methylhistamine, Urine (MHISTA)]. Cautions: While an average North American diet has no effect on urinary N-methylhistamine (NMH) levels, mild elevations (approximately 30%) may be observed on very histamine-rich diets. This problem is more pronounced if random urine specimens are used and collected following a histamine-rich meal. NMH levels may be depressed in individuals who have an alteration in the histamine-N-methyl transferase gene, which encodes the enzyme that catalyzes NMH formation. This alteration results in an amino acid change that decreases the rate of NMH synthesis. When N-acetylcysteine is administered at levels sufficient to act as an antidote for the treatment of acetaminophen overdose, it may lead to falsely decreased creatinine results.