Last Modified:
11/15/2019 6:45:22 AM
Specimen Requirements:
4.0 mL random Urine collection in a Plastic Container
Collection Instructions:
Refrigerate specimen after collection and send specimen refrigerated or frozen; do not add any preservative
Minimum Volume:
1.0 mL Urine
Transport & Storage: Temperature/Stability:
24 hours Ambient
8 days Refrigerated (preferred)
14 days Frozen
Reference Range:
0-5 years: 120-510 mcg/g creatinine
6-16 years: 70-330 mcg/g Creatinine
>16 years: 30-200 mcg/g creatinine
Test Comments:
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.
Methodology:
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) & Enzymatic Colorimetric Assay
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
Monitoring therapeutic progress in conditions that are associated with secondary, localized, low-grade persistent, mast-cell proliferation and activation such as interstitial cystitis
Custom Panel:
No
PRODUCTION SCHEDULE
Turn Around Time:
3 to 7 days
Days Performed:
Tuesday, Thursday
Sites Performed:
Mayo Laboratory
PHL Test Code:
MSOT
EPIC Test Code:
MISC
Send Out Test Code:
NMHIN
Alternate Test Names:
1-Methylhistamine; Histamine Metabolites; N-Methylhistamine, U; Urinary N-Methylhistamine
CPT Coding:
82542
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