How are plasma metanephrine and catecholamine testing used to diagnose pheochromocytoma?

Updated: Aug 10, 2018
  • Author: Michael A Blake, MBBCh, MRCPI, FRCR; Chief Editor: George T Griffing, MD  more...
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Answer

A fractionated plasma free metanephrine level may be measured in a standard venipuncture sample, drawn about 15-20 minutes after intravenous catheter insertion. Positioning of the patient for the venipuncture is controversial. Although some experts advocate having the patient seated, NANETS guidelines recommend drawing the sample with the patient in a supine position, as tests in seated patients have a higher false-positive rate. [35]

Perform a 24-hour urine collection for creatinine, total catecholamines, vanillylmandelic acid, and metanephrines. Measure creatinine in all collections of urine to ensure adequacy of the collection. The collection container should be dark and acidified and should be kept cold to avoid degradation of the catecholamines. Optimally, collect urine during or immediately after a crisis.


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