N-Methylhistamine, Urine
Test Mnemonic
MHISTA
CPT Codes
- 82542 - QTY (1)
Aliases
- Methylhistamine-N, Urine
- Methylhistamine-N, Urine
- N-Methylhistamine, 24 Hour, Urine
- N-Methylhistamine, 24 Hour, Urine
- NMH
- NMH
Includes
- N-Methylhistamine, 24 Hr
- Creatinine, 24 Hr Urine mg/24 h
- Collection Duration
- Urine Volume
- Creatinine Concentration, 24 Hr Urine mg/dL
Performing Laboratory
Mayo Clinic Dpt of Lab Med & Pathology
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 5 mL | Urine, 24-hour (well-mixed) | Clean container | Refrigerate during collection. | Refrigerated | Please include volume and hours of collection. |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 3 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Refrigerated | 28 days (preferred) |
| Ambient | 14 days |
| Frozen | 28 days |
Days Performed
Tue, Thu
Turnaround Time
4 - 8 days
Methodology
| Name | Description |
|---|---|
| Colorimetric Enzyme Assay | |
| Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) |
Reference Range
Special Info
Patient must not be taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine as these medications increase N-methylhistamine (NMH) levels. Random urine collections are preferred for patients with episodic symptoms, for example in the context of allergic reactions, brought on by specific environmental factors. Please refer to N-Methylhistamine, Random, Urine (UMHISR).
Clinical Info
This test is 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 24-hour urine collection specimens. Monitoring therapeutic progress in conditions that are associated with secondary, localized, low-grade persistent, mast-cell proliferation and activation such as interstitial cystitis. 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.