N-Methylhistamine, 24 Hour, Urine

Test Code

39559

CPT Codes
82542, 82570

Preferred Specimen

5 mL aliquot of urine collected in 24-hour no preservative container

Patient Preparation
Patient must not be taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine as these medications increase N-methylhistamine (NMH) levels.

Minimum Volume

3 mL

Other Acceptable Specimens

Aliquot from a 24-hour urine preserved in 50% Acetic acid, Boric Acid, 6M hydrochloric acid, 6M nitric acid, or sodium carbonate container, collected in a urine container

Instructions

1. Collect urine for 24 hours
2. No preservative
3. Aliquot into plastic tube and send at refrigerate temperature

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

Random urine collections are preferred for patients with episodic symptoms, for example in the context of allergic reactions, brought on by specific environmental factors. See 39604 N-Methylhistamine, Random, Urine.

If ordering this test with 39559- N-Methylhistamine, 24 Hour, Urine/10109- 2,3-Dinor-11 Beta-Prostaglandin F2 Alpha, 24 Hour, Urine; both tests must be ordered under a different order number. They cannot share an order number.

If the total volume provided is less than 300 mL, this test will be canceled and NMHR will be ordered and performed.

Transport Temperature

Refrigerated (cold packs)

Specimen Stability

Room temperature: 14 days
Refrigerated: 28 days
Frozen: 28 days

Methodology
NMH1D: Liquid Chromatography-Tandem Mass Spectrometry
CRT24: Enzymatic Colorimetric Assay

Setup Schedule

Set up: Tues, Thurs; Report available: 3 days

Reference Range

See Laboratory Report

Clinical Significance

Screening for and monitoring of mastocytosis and disorders of systemic mast-cell activation, such as anaphylaxis and other forms of severe systemic allergic reactions using 24-hour urine collection specimens. Monitoring therapeutic progress in conditions that are associated with secondary, localized, low-grade persistent, mast-cell proliferation and activation such as interstitial cystitis.

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-methyl transferase gene, 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.

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.