N‑Methylhistamine, 24 Hour, Urine
Use
Screening for and monitoring of mastocytosis and disorders of systemic mast‑cell activation, such as anaphylaxis and severe systemic allergic reactions, using 24‑hour urine collection specimens. Also useful for monitoring therapeutic progress in conditions with secondary, localized, low‑grade persistent mast‑cell proliferation and activation such as interstitial cystitis.
Special Instructions
Ordering guidance indicates that if total volume provided is less than 300 mL, the test will be canceled and NMHR (random) ordered and performed. Patient must not be taking MAOIs or aminoguanidine, as these increase NMH levels. Includes two component assays as always performed: NMH1D and CRT24.
Limitations
NMH levels may not be elevated in all patients with systemic mastocytosis or anaphylaxis; there is overlap between UP and systemic disease, and results should not be used alone to distinguish. Up to 25 % variability in random urine excretion is possible, making 24‑hour collections preferable. Diets rich in histamine may increase NMH by ~30 %, especially with random specimens. Genetic variation in HNMT may depress NMH levels. N‑acetylcysteine may falsely lower creatinine results.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 44340-8
- 44340-8
Result Turnaround Time
3-7 days
Related Documents
For more information, please review the documents below
Specimen
Urine
Volume
5 mL
Minimum Volume
1.75 mL
Container
Plastic, 5‑mL tube
Collection Instructions
Collect urine for 24 hours; no preservative; aliquot into plastic tube and send refrigerated.
Patient Preparation
Patient must not be taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine.
Causes for Rejection
If total volume provided is less than 300 mL the test will be canceled.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 28 days |
| Frozen | 28 days |