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HelpTEST ID NMHR N-Methylhistamine, Random, Urine
Reporting Name
N-Methylhistamine, Random, USpecimen Type
UrineOrdering 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: Patients taking monoamine oxidase inhibitors (MAOIs) may have increased levels of N-methylhistamine. If medically feasible, for 2 weeks before specimen collection, patient should not take MAOIs.
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Container/Tube: Plastic vial
Specimen Volume: 5 mL
Collection Instructions:
1. Within a few hours of symptom onset, collect a random urine specimen.
2. No preservative.
Specimen Minimum Volume
3 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Urine | Refrigerated (preferred) | 28 days |
| Frozen | 28 days | |
| Ambient | 14 days |
Method Name
NMHR1: Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
CRETR: Enzymatic Colorimetric Assay
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Reference Values
N-METHYLHISTAMINE
0-5 years: 85-369 mcg/g creatinine
6-16 years: 48-238 mcg/g creatinine
>16 years: 19-143 mcg/g creatinine
CREATININE
≥18 years old: 16-326 mg/dL
Reference values have not been established for patients who are younger than 18 years.
Day(s) Performed
Monday, Wednesday, Friday
Report Available
3 to 7 daysSpecimen Retention Time
14 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
82542
82570
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 |
Clinical Information
N-methylhistamine (NMH) is the major metabolite of histamine, which is produced by mast cells. Increased histamine production is seen in conditions associated with increased mast-cell activity, such as allergic reactions, but also in mast-cell proliferation disorders, particularly mastocytosis.
Mastocytosis is a rare disease. Its most common form, urticarial pigmentosa (UP), affects the skin and is characterized by multiple persistent small reddish-brown lesions that result from infiltration of the skin by mast cells. Systemic mastocytosis (SM) is caused by the accumulation of mast cells in other tissues and can affect organs such as the liver, spleen, bone marrow, and small intestine. The mast-cell proliferation in CM can be either benign or malignant. In children, benign systemic mastocytosis tends to resolve over time, while in most adults, the disease is progressive. SM may or may not be accompanied by UP.(1,2) Patients with UP or SM can have symptoms ranging from itching, gastrointestinal distress, bone pain, and headaches; to flushing and anaphylactic shock.
Definitive diagnosis of SM is made by bone marrow biopsy; however, patients with SM also usually exhibit elevated levels of NMH.(1-5) Other biochemical markers include 11-beta prostaglandin F2 alpha, a metabolite of prostaglandin D2 (23BPR / 2,3-Dinor 11 Beta-Prostaglandin F2 Alpha, Random, Urine) and tryptase, alpha or beta (TRYPT / Tryptase, Serum). Histamine in blood or urine is also sometimes measured, but it generally has less diagnostic value than NMH measurement in urine, in particular if measurements in blood are not undertaken during a spell.
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.
N-methylhistamine 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.
N-methylhistamine levels may be decreased in individuals who are receiving drugs that inhibit diamine oxidase.
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.
Patients taking monoamine oxidase inhibitors (MAOIs) may have increased levels of NMH. If medically feasible, for 2 weeks before specimen collection, MAOIs should not be taken.
Method Description
N-methylhistamine:
Isotopically labeled N-methylhistamine (NMH) is added to the sample as an internal standard (IS). NMH and IS are then purified from urine using solid phase extraction. The eluate is analyzed using liquid chromatography-tandem mass spectrometry. (Unpublished Mayo method)
Creatinine:
The enzymatic method is based on the determination of sarcosine from creatinine with the aid of creatininase, creatinase, and sarcosine oxidase. The liberated hydrogen peroxide is measured via a modified Trinder reaction using a colorimetric indicator. Optimization of the buffer system and the colorimetric indicator enables the creatinine concentration to be quantified both precisely and specifically.(Package insert: Creatinine plus Ver 2. Roche Diagnostics; V15.0, 03/2019)