3mL EDTA blood
Recommended collection: Draw from fasting patient at supine position after 20-30min of rest
Keep cold with ice and send immediately to the laboratory.
Liquid Chromatography - Tandem Mass Spectrometry (LC-MS/MS)
From 0 day:Metanephrine : < 0.33 nmol/LNormetanephrine : < 0.71 nmol/L Plasma metanephrine and normetanephrine reference intervals (URL 97.5th percentile value) are from Eisenhofer et.al 2013 Annals Clin Biochem 50:62-69; above URLs used together demonstrated 93.9% sensitivity and 88.3% specificity.
Mean = 7 days, Range: 3 – 11 days
Studies have suggested that age-specific / age-group specific reference intervals for plasma normetanephrine used in conjunction with metanephrine improved specificity and sensitivity for the diagnosis of phaechromocytoma. A curvilinear algorithm equation to calculate age-specific reference intervals for plasma normetanephrines was derived by Eisenhofer et.al (2013). Age-group specific reference intervals (using the first age of each group) obtained from the curvilinear algorithm is reproduced here. Used together with plasma metanephrine URL of 0.45 nmol/L has demonstrated 93.6% sensitivity and 96% specificity 5-17yr: 0.54 nmol/L 18-29yr: 0.55 nmol/L 30-39yr: 0.60 nmol/L 40-49yr: 0.67 nmol/L 50-59yr: 0.80 nmol/L >60yr: 0.99 nmol/L Rao et.al 2017 Eur J Endocrinol 177:103-113 using LC-MS/MS in their study verified the use of age-specific reference intervals (NMET) in diagnosis. Additionally, the use of methoxytyramine (MTY) assists with positive confirmation.Patient Preparation: Subjects should abstain from caffeine, acetoaminophen, before testing. The following drugs: (on MET, NMET, MTY) isoproterenol, ephedrine, (on MTY) metamphetamine also interferes with the analysis technique.