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HelpTest Code NMHR1 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. See NMH24 / N-Methylhistamine, 24 Hour, Urine.
Specimen Required
Only orderable as part of a profile. For more information see NMHR / N-Methylhistamine, Random, Urine.
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, 5-mL tube
Specimen Volume: 5 mL
Collection Instructions:
1. Collect a random urine specimen.
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 as a part of a random urine collection profile
Monitoring therapeutic progress in conditions that are associated with secondary, localized, low-grade persistent, mast-cell proliferation and activation such as interstitial cystitis
Method Name
Only orderable as part of a profile. For more information see NMHR / N-Methylhistamine, Random, Urine.
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
N-Methylhistamine, RandomSpecimen Type
UrineSpecimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 28 days | |
| Ambient | 28 days | ||
| Frozen | 28 days |
Reference Values
Only orderable as part of a profile. For more information see NMHR / N-Methylhistamine, Random, Urine.
0-5 years: 120-510 mcg/g creatinine
6-16 years: 70-330 mcg/g creatinine
>16 years: 30-200 mcg/g creatinine
Interpretation
Increased concentrations of urinary N-methylhistamine (NMH) are consistent with urticaria pigmentosa (UP), systemic mastocytosis, or mast-cell activation. Because of its longer half-life, urinary NMH measurements have superior sensitivity and specificity than histamine, the parent compound. However, not all patients with systemic mastocytosis or anaphylaxis will exhibit concentrations outside the reference range and healthy individuals may occasionally exhibit values just above the upper limit of normal.
The extent of the observed increase in urinary NMH excretion is correlated with the magnitude of mast-cell proliferation and activation, UP patients, or patients with other localized mast-cell proliferation and activation, show usually only mild elevations, while systemic mastocytosis and anaphylaxis tend to be associated with more significant rises in NMH excretion (2-fold or more). There is, however, significant overlap in values between UP and systemic mastocytosis, and urinary NMH measurements should not be relied upon alone in distinguishing localized from systemic disease.
Up to 25% variability in random-urine excreted levels may be observed, making 24-hour urine collections preferable for cases with borderline results.
Children have higher NMH levels than adults. By the age of 16, adult levels have been reached.
Clinical Reference
1. Roberts LJ II, Oates JA. Disorders of vasodilator hormones: the carcinoid syndrome and mastocytosis. In: Wilson JD, Foster DW, eds. Williams Textbook of Endocrinology. 8th ed. WB Saunders Company;1992:1625-1634
2. Akin C, Metcalfe DD. Mastocytosis. In: Leung DYM, Greaves MW, eds. Allergic Skin Disease: A Multidisciplinary Approach. Marcel Dekker, Inc.:2000:337-352
3. Keyzer JJ, de Monchy JG, van Doormaal JJ, van Voorst Vader PC. Improved diagnosis of mastocytosis by measurement of urinary histamine metabolites. N Engl J Med. 1983;309(26):1603-1605
4. Heide R, Riezebos P, van Toorenbergen AW, et al. Predictive value of urinary N-methylhistamine for bone marrow involvement in mastocytosis. J Invest Dermatol. 2000;115(3):587
5. Van Gysel D, Oranje AP, Vermeiden I, et al. Value of urinary N-methylhistamine measurements in childhood mastocytosis. J Am Acad Derm. 1996;35(4):556-558
6. Divekar R, Butterfield J. Urinary 11b-PGF2a and N-methyl histamine correlate with bone marrow biopsy findings in mast cell disorders. Allergy. 2015;70(10):1230-1238. doi:10.1111/all.12668
7. Butterfield J, Weiler CR: The utility of measuring urinary metabolites of mast cell mediators in systemic mastocytosis and mast cell activation syndrome. J Allergy Clin Immunol Pract. 2020;8(8):2533-2541. doi:10.1016/j.jaip.2020.02.021
Day(s) Performed
Monday, Wednesday, Friday
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
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| NMHR1 | N-Methylhistamine, Random | 13781-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 605015 | N-Methylhistamine, Random, U | 13781-0 |
Report Available
3 to 7 daysSpecimen Minimum Volume
3 mL