N Methylhistamine, Random Urine (Sendout)

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General Information

Lab Name
N Methylhistamine, Random Urine (Sendout)
Lab Code
RURNMH
Epic Name
N-Methylhistamine, Random Urine (Sendout)
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].

        References
        Synonyms
        1-Methylhistamine, MIAA-Urine, N-methylhistamine, N-Methylimidazoleacetic Acid-Urine, NMHR
        Components
        Code Name
        RURNMR N Methylhistamine, Random Urine
        RUCRER Creatinine, Random Urine

        Interpretation

        Method

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

        Creatinine: Enzymatic Colorimetric Assay

        Reference Range
        See individual components
        Ref. Range Notes

        Reference Values:

        N-Methylhistamine, Random Urine:

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

        Creatinine, Random Urine:

        Age: Range:
        >=18 years: 16-326 mg/dL
        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.

            References

            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 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 while awaiting shipment. Transport with a cold pack.
            • 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.

            Sendouts:

            • Order Mayo Test: NMHR
            • Interfaced: Yes [Interface: 601; Worksheet: MARF]

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

            Misc Sendout

            Performance

            Lab Department
            Sendouts Mayo Lab (RF)(MARF)
            Frequency
            Performed: Monday, Wednesday, Friday. Reported: 3-7 days from sample receipt at Mayo Clinic Lab.
            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

            CPT Codes
            82542, 82570
            LOINC
            13781-0
            Interfaced Order Code
            UOW6220