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Test Code
NMH24
Test Name
N-Methylhistamine, 24 Hour
CPT Codes
82542
Included Tests
  • Creatinine, 24 HR
  • Creatinine Concentration, 24 HR
  • N-Methylhistamine, 24 Hr
Expected Turnaround Time
3 - 7 days
Clinical Utility
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.
Specimen and Container Info

Specimen Type: 24 Hour Urine

  

Collection Container: 24 Hour Plastic Urine Container

    

Desired Specimen Volume: 5 mL
Collection Instructions
  1. Collect 24-hour urine in a timed urine collection jug.
Processing and Submission Instructions
  1. Transfer 5 mL of urine into clear aliquot tubes (screw caps).
  2. Specimen volume (in milliliters) and duration are required.
  3. Total volume must be at least 300 mL for 24-hour collections.
Patient Preparation
Patient must not be taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine as these medications increase N-methylhistamine (NMH) levels.
Transport Instructions

Transport to the laboratory refrigerated. 
Stability Requirements

Room Temperature

14 days

Refrigerated

28 days

Frozen

28 days
Methodology
Liquid Chromatography-Tandem Mass Spectrometry/Enzymatic Colorimetric Assay
Reference Intervals

See patient report.
Limitations

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.
Alternate Names
  • 1-Methylhistamine
  • Histamine Metabolites
  • Urinary N-Methylhistamine
Reference Lab
Mayo Clinic Laboratories
Testing Schedule
Routine, 2 times per week
The American Medical Association (AMA) Current Procedural Terminology (CPT) codes published by HNL Lab Medicine are guidelines and are intended for informational purposes only. CPT coding is the exclusive responsibility of the billing entity. View the Terms.
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