N-Methyl Histamine (MIAA), Random Urine (Sendout)

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General Information

Lab Name
Lab Code
478
External Test Id
NMHR
Description

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
  • Monitoring therapeutic progress in conditions that are associated with secondary, localized, low-grade persistent, mast-cell proliferation and activation such as interstitial cystitis

Patient Preparation:

  • Patient must not be taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine, as these medications increase N-methylhistamine (NMH) levels.
  • Patient should avoid consuming histamine-rich food 24 hours prior to/during collection (e.g., cheese, chicken, liver, eggplant, sauerkraut, sirloin steak, spinach, tomatoes, wine, or yogurt).

Ordering Requirements: Test pre-approved for orders originating from Fred Hutch, UW Medicine, or The Vancouver Clinic Allergy Clinics (MSALL, UESALL, VANTVC). Orders from other locations require Laboratory Medicine Resident (LMR) approval.

Ordering Note: This test is for random urine specimens only. For timed collections, refer to N Methylhistamine, 24 Hour Urine (Sendout) [RUNMHT].

Synonyms
1-Methylhistamine, MIAA-Urine, N-methylhistamine, N-Methylimidazoleacetic Acid-Urine, NMHR
Components

Interpretation

Method

N-Methylhistamine: Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Creatinine: Enzymatic Colorimetric Assay

Reference Range
Ref. Range Notes

Reference Ranges:

Age: N-Methylhistamine Range:
0-5 years 120-510 mcg/g creatinine
6-16 years 70-330 mcg/g creatinine
>16 years 30-200 mcg/g creatinine
Interferences and Limitations

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.

Ordering & Collection

Specimen Type
Urine
Collection

Within a few hours of symptom onset, collect a random urine specimen in a preservative-free collection container.

Approval Required
Test pre-approved for orders originating from Fred Hutch, UW Medicine, or The Vancouver Clinic Allergy Clinics (MSALL, UESALL, VANTVC). Orders from all other locations require Laboratory Medicine Resident (LMR) approval.
Handling Instructions

Outside Laboratories:

  • Aliquot 5 mL urine to a plastic screw-cap vial and refrigerate specimen.
  • Indicate "random collection" on the DLMP requisition.

Stability: Refrigerated (Preferred): 28 days; Frozen: 28 days; Ambient: 14 days.

Quantity
Requested: 5 mL urine
Minimum: 3 mL urine

Processing

Receiving Instructions

Aliquot 5 mL urine into a plastic, screw-capped vial and refrigerate.

Login: SEND1-;REFRIG

  • RSNDT1: MAYO
  • RSTYP1: URN-RAND
  • RTSRQ1: ;N Methylhistamine, Random Urine (Mayo Test NMHR)

Sendouts,

  • Order Mayo Test: NMHR.

Stability: Refrigerated (preferred): 28 days; Frozen: 28 days; Ambient: 14 days.

Misc Sendout

Performance

Lab Department
Frequency
Performed: Tuesday, Thursday. Report Available: 3-7 days.
Available STAT?
No
Performing Location(s)
Sendout Mayo Clinic Laboratories
800-533-1710

200 First Street Southwest
Rochester, MN 55901
Sendout Mayo Clinic Laboratories (Superior Drive)
800-533-1710

3050 Superior Drive NW
Rochester, MN 55901

Billing & Coding

Billing Comments

CPT: 82542