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Test Code NMH1D N-Methylhistamine, 24 Hour, Urine


Ordering Guidance


Random urine collection is preferred for patients with episodic symptoms, eg, in the context of allergic reactions, brought on by specific environmental factors; order NMHR / N-Methylhistamine, Random, Urine.



Specimen Required


Only orderable as part of a profile. For more information see NMH24 / N-Methylhistamine, 24 Hour, Urine.

 

Patient Preparation: Patient must not be taking monoamine oxidase inhibitors (MAOIs) 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 urine for 24 hours.

2. No preservative.

3. Aliquot into plastic tube and send at refrigerate temperature.


Secondary ID

605159

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 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 NMH24 / N-Methylhistamine, 24 Hour, Urine.

 

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

N-Methylhistamine, 24 Hr, U

Specimen Type

Urine

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days

Reject Due To

  All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

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, urticaria 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 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 systemic mastocytosis can be either benign or malignant. In children, benign systemic mastocytosis tends to resolve over time, while in most, but not all adults, the disease is progressive. Systemic mastocytosis may or may not be accompanied by UP.(1,3) Patients with UP or systemic mastocytosis can have symptoms ranging from itching, gastrointestinal distress, bone pain, and headaches; to flushing and anaphylactic shock.

 

Definitive diagnosis of mastocytosis is made by bone marrow biopsy; however, patients with systemic mastocytosis usually exhibit elevated levels of NMH.(1-5) Other biochemical markers include 11-beta prostaglandin F(2) alpha, a metabolite of prostaglandin D2 (23BPT / 2,3-Dinor 11 Beta-Prostaglandin F2 Alpha, 24 Hour, Urine), and alpha or beta tryptase (TRYPT / Tryptase, Serum).

Reference Values

Only orderable as part of a profile. For more information see NMH24 / N-Methylhistamine, 24 Hour, 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 years, adult levels have been reached.

Day(s) Performed

Monday, Wednesday, Friday

Specimen Retention Time

14 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

LOINC Code Information

Test ID Test Order Name Order LOINC Value
NMH1D N-Methylhistamine, 24 Hr, U 44340-8

 

Result ID Test Result Name Result LOINC Value
605159 N-Methylhistamine, 24 Hr 44340-8

Report Available

3 to 7 days

Specimen Minimum Volume

3 mL