Liquid Chromatography - Tandem Mass Spectrometry (LC-MS/MS)
Screening test for presumptive diagnosis of catecholamine-secreting pheochromocytomas or paragangliomas.
Metanephrine, Plasma <0.5 nmol/L
Normetanephrine, Plasma <0.9 nmol/L
While most circulating metanephrines are derived directly from adrenal secretion, peripheral conversion of catecholamines makes a small contribution. Therefore, substances that increase endogenous catecholamine levels can result in borderline elevations of plasma metanephrines. These include monamine oxidase inhibitors (MOIs), catecholamine reuptake inhibitors, and some anesthetic gases, particularly halothane. Artifactually decreased plasma metanephrine levels may be observed when patients are already receiving metyrosine treatment.
- Normetanephrines, Plasma
- Fractionated Metanephrines, Plasma
- Metanephrines, Fract., Free, P
Collect specimen in a lavender top tube. Centrifuge, aliquot plasma into a plastic vial and freeze. Discontinue epinephrine and epinephrine-like drugs at least 1 week before obtaining the specimen. The patient must fast and abstain from smoking tobacco for at least 4 hours before the specimen is drawn. The patient may drink only water during the fasting period.