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HelpTest Code NMHRSO N-Methylhistamine, Random, Urine
Additional Codes
Mayo Test Code: NMHR
Ordering Guidance
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. order NMH24 / N-Methylhistamine, 24 Hour, Urine.
If ordering this test with 23BPR / 2,3-Dinor 11 Beta-Prostaglandin F2 Alpha, Random, Urine, both tests must be ordered under different order numbers. They cannot share an order number.
Specimen Required
Patient Preparation: Patient must not be taking monoamine oxidase inhibitors (MAOI) or aminoguanidine as these medications increase N-methylhistamine (NMH) levels.
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Container/Tube: Plastic vial
Specimen Volume: 5 mL
Collection Instructions:
1. Collect a random urine specimen within a few hours of symptom onset.
2. No preservative.
Useful For
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
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| NMHR1 | N-Methylhistamine, Random | No | Yes |
| CRETR | Creatinine, Random, U | No | Yes |
Method Name
NMHR1: Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
CRETR: Enzymatic Colorimetric Assay
Reporting Name
N-Methylhistamine, Random, USpecimen Type
UrineSpecimen Minimum Volume
3 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Urine | Refrigerated (preferred) | 28 days |
| Frozen | 28 days | |
| Ambient | 14 days |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Reference Values
0-5 years: 120-510 mcg/g creatinine
6-16 years: 70-330 mcg/g creatinine
>16 years: 30-200 mcg/g creatinine
Cautions
While an average North American diet has no effect on urinary N-methylhistamine (NMH) levels, mild elevations (around 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-methyltransferase gene (HNMT), 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.
Day(s) Performed
Monday, Wednesday, Friday
Report Available
3 to 7 daysSpecimen Retention Time
14 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82542
82570
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| NMHR | N-Methylhistamine, Random, U | 13781-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 605015 | N-Methylhistamine, Random, U | 13781-0 |
| CRETR | Creatinine, Random, U | 2161-8 |