N-Methylhistamine, 24 Hour Urine
Order Code:
NMHIN
Test Summary
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
Aliases
- Mayo code NMH24
Specimen Collection
Special Instructions
N/A
Preferred Specimen
5 mL of 24 hour urine
Minimum Volume
3 mL
Instructions
Collection Instructions:
1. Collect urine for 24 hours.
2. No preservative.
3. Aliquot into plastic tube and send at refrigerate temperature.
If ordering this test with 23BPT / 2,3-Dinor 11 Beta-Prostaglandin F2 Alpha, 24 Hour, Urine, both tests must be ordered under different order number. They cannot share an order number.
1. Collect urine for 24 hours.
2. No preservative.
3. Aliquot into plastic tube and send at refrigerate temperature.
If ordering this test with 23BPT / 2,3-Dinor 11 Beta-Prostaglandin F2 Alpha, 24 Hour, Urine, both tests must be ordered under different order number. They cannot share an order number.
Patient Preparation
Patient must not be taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine as these medications increase N-methylhistamine (NMH) levels.
Storage
Plastic screw-cap vial
Transport Temperature
Refrigerated
Specimen Stability
- Room Temperature: 14 days
- Refrigerated: 28 days
- Frozen: 28 days
Limitations
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-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.
Other Acceptable Specimens
N/A
Unacceptable Specimens
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.
Order Code
NMHIN
EPIC (Premier) Code
LAB6042
Includes
N-Methylhistamine,
24 Hr, U;
Creatinine, 24 HR, U
24 Hr, U;
Creatinine, 24 HR, U
CPT Code
- 82542
Billing Code
- 650024
CPT Statement
Methodology
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) and Enzymatic Colorimetric Assay
FDA Status
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.
Physician Attestation of Informed Consent
N/A
Testing Laboratory
Mayo Clinic Laboratories
200 First Street SW
Rochester MN, 55905
200 First Street SW
Rochester MN, 55905
Department
Reference Testing
Reference Range
N/A
Setup Schedule / Expected Turnaround Time
Monday, Wednesday, Friday; Reports available: 3 - 7 days
Specimen Collection
Special Instructions
N/A
Preferred Specimen
5 mL of 24 hour urine
Minimum Volume
3 mL
Instructions
Collection Instructions:
1. Collect urine for 24 hours.
2. No preservative.
3. Aliquot into plastic tube and send at refrigerate temperature.
If ordering this test with 23BPT / 2,3-Dinor 11 Beta-Prostaglandin F2 Alpha, 24 Hour, Urine, both tests must be ordered under different order number. They cannot share an order number.
1. Collect urine for 24 hours.
2. No preservative.
3. Aliquot into plastic tube and send at refrigerate temperature.
If ordering this test with 23BPT / 2,3-Dinor 11 Beta-Prostaglandin F2 Alpha, 24 Hour, Urine, both tests must be ordered under different order number. They cannot share an order number.
Patient Preparation
Patient must not be taking monoamine oxidase inhibitors (MAOIs) or aminoguanidine as these medications increase N-methylhistamine (NMH) levels.
Storage
Plastic screw-cap vial
Transport Temperature
Refrigerated
Specimen Stability
- Room Temperature: 14 days
- Refrigerated: 28 days
- Frozen: 28 days
Limitations
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-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.
Other Acceptable Specimens
N/A
Unacceptable Specimens
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.
Result Information
Methodology
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) and Enzymatic Colorimetric Assay
Testing Laboratory
N/A
Reference Range
N/A
Setup Schedule / Expected Turnaround Time
Monday, Wednesday, Friday; Reports available: 3 - 7 days