N-Methylhistamine, Random, Urine
Use
Screening for and monitoring of 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. Increased concentrations of urinary N‑methylhistamine (NMH) are consistent with urticaria pigmentosa (UP), systemic mastocytosis, or mast‑cell activation. Urinary NMH measurements have superior sensitivity and specificity than histamine. Up to 25% variability may be observed in random‑urine excreted levels, making 24‑hour urine collections preferable for borderline results. Children have higher NMH levels than adults; by age 16, adult levels are reached. Reference intervals: 0‑5 years: 120‑510 mcg/g creatinine; 6‑16 years: 70‑330 mcg/g creatinine; >16 years: 30‑200 mcg/g creatinine. (Mayo Clinic Laboratories)
Special Instructions
Patient must not be taking monoamine oxidase inhibitors (MAOI) or aminoguanidine as these medications increase NMH levels.
Limitations
Not all patients with systemic mastocytosis or anaphylaxis will exhibit concentrations outside the reference range; healthy individuals may occasionally exhibit values just above the upper limit of normal. There is significant overlap in values between UP and systemic mastocytosis; NMH measurements should not be relied upon alone. Up to 25% variability in random‑urine excreted levels may be observed. Mild elevations (around 30%) may occur on histamine‑rich diets, especially with random‑urine specimens. NMH levels may be depressed in individuals with alterations in the histamine‑N‑methyltransferase gene (HNMT). N‑acetylcysteine may lead to falsely decreased creatinine results.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 13781-0
- 13781-0
- 2161-8
Result Turnaround Time
3-7 days
Related Documents
For more information, please review the documents below
Specimen
Urine
Volume
5 mL
Minimum Volume
3 mL
Container
Plastic vial (Sarstedt Aliquot Tube, 5 mL (T914))
Collection Instructions
Collect a random urine specimen within a few hours of symptom onset. No preservative.
Patient Preparation
Patient must not be taking monoamine oxidase inhibitors (MAOI) or aminoguanidine.
Causes for Rejection
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | Ambient: 14 days |
| Refrigerated | Refrigerated (preferred): 28 days |
| Frozen | Frozen: 28 days |