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Test Code 0234398 N-Methylhistamine, Urine

Additional Codes

 

Mayo Test ID
NMHIN

 

Performing Laboratory

Mayo Clinic Laboratories in Rochester

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

Method Name

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

NCTU: Enzymatic Colorimetric Assay

Reporting Name

N-Methylhistamine, U

Specimen Type

Urine


Advisory Information


Individuals who are taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine would have increased N-methylhistamine (NMH) results, which would be uninterpretable.



Specimen Required


Supplies: Aliquot Tube, 5 mL (T465)

Container/Tube: Plastic, 5-mL tube (T465)

Specimen Volume: 5 mL

Collection Instructions:

1. Collect urine for 24 hours.

2. No preservative.

Additional Information:

1. 24-Hour collection is preferred, but a random specimen is also acceptable.

2. See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens in Special Instructions for multiple collections.


Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Refrigerated (preferred) 8 days
  Frozen  14 days
  Ambient  24 hours

Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

NA

Reference Values

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 spot-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.

Day(s) and Time(s) Performed

Tuesday, Thursday; 10 a.m.

Analytic Time

3 days

Specimen Retention Time

14 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

82542

LOINC Code Information

Test ID Test Order Name Order LOINC Value
NMHIN N-Methylhistamine, U 44340-8

 

Result ID Test Result Name Result LOINC Value
NCTU_ Creatinine Conc 20624-3
21589 N-Methylhistamine, U 44340-8
TM73 Collection Duration 13362-9
VL63 Urine Volume 3167-4

Profile Information

Test ID Reporting Name Available Separately Always Performed
NMH N-Methylhistamine, U No Yes
NCTU Creatinine Concentration No Yes

Urine Preservative Collection Options

Note: The addition of preservative or application of temperature controls must occur within 4 hours of completion of the collection.

Ambient

Yes

Refrigerated

Preferred

Frozen

Yes

6N HCl

Yes

50% Acetic Acid

Yes

Na2CO3

Yes

Toluene

No

6N HNO3

Yes

Boric Acid

Yes

Thymol

No

Diazolidinyl

No