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Test Code LAB14864 N-Methylhistamine, Random, Urine


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: 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.


Secondary ID

604981

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, U

Specimen Type

Urine

Specimen 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

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.

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.

Day(s) Performed

Monday, Wednesday, Friday

Report Available

3 to 7 days

Performing 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

NY State Approved

Yes