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Division of Endocrinology and Metabolism, Department of Medicine III, and
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Department of Surgery, University of Vienna Medical School, A-1090 Vienna, Austria.
aAddress correspondence to this author at: Division of Endocrinology and Metabolism, Department of Internal Medicine III, University of Vienna Medical School, Währinger Gürtel 18-20, A-1090 Vienna, Austria. Fax 43-1-40400-7790; e-mail michael.roden{at}akh-wien.ac.at.
Background: Pheochromocytoma is a rare cause of hypertension resulting from increased catecholamine secretion. We aimed to develop a method to measure unconjugated plasma normetanephrine (NMN) and metanephrine (MN) without interference from acetaminophen, a widely prescribed drug for headaches.
Methods: Plasma samples were obtained from 48 subjects (23 males, 25 females; mean age, 49 ± 14 years; hypertension, n = 37) under resting conditions. Following extraction on solid-phase cation-exchange columns, unconjugated metanephrines were analyzed by HPLC with electrochemical detection and with 4-hydroxy-3-methoxybenzylamine as an internal standard. Catecholamines were measured by HPLC.
Results: The assays were linear up to 2000 pg for NMN and for MN. Intraassay imprecisions (CVs) were 4.7% for NMN and 7.0% for MN, and the interassay CV was 12% for both NMN and MN. The limit of detection was 11 fmol for NMN and 17 fmol for MN. Ingestion of acetaminophen or its addition to plasma did not interfere with the MN peaks. Plasma NMN and MN were positively correlated (r = 0.52 and 0.49, respectively; P <0.01 for both) with the respective catecholamines. Plasma NMN (r = 0.27; P = 0.02) but not MN positively correlated with age, whereas only plasma catecholamines (and not metanephrines) were positively correlated (P <0.05) with diastolic blood pressure.
Conclusions: This sensitive MN assay is not affected by simultaneous acetaminophen medication, and reveals a correlation of metanephrines with plasma and urinary catecholamines and age but not with blood pressure.
The following articles in journals at HighWire Press have cited this article:
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  W. H.A. de Jong, K. S. Graham, J. C. van der Molen, T. P. Links, M. R. Morris, H. A. Ross, E. G.E. de Vries, and I. P. Kema Plasma Free Metanephrine Measurement Using Automated Online Solid-Phase Extraction HPLC Tandem Mass Spectrometry Clin. Chem., September 1, 2007; 53(9): 1684 - 1693. [Abstract] [Full Text] [PDF]
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J. J. Willemsen, C.G.J. Sweep, J. W.M. Lenders, and H. A. Ross Stability of Plasma Free Metanephrines during Collection and Storage as Assessed by an Optimized HPLC Method with Electrochemical Detection Clin. Chem., November 1, 2003; 49(11): 1951 - 1953. [Full Text] [PDF]
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 Y. C. Kudva, A. M. Sawka, and W. F. Young Jr. The Laboratory Diagnosis of Adrenal Pheochromocytoma: The Mayo Clinic Experience J. Clin. Endocrinol. Metab., October 1, 2003; 88(10): 4533 - 4539. [Full Text] [PDF]
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R. L. Taylor and R. J. Singh Validation of Liquid Chromatography-Tandem Mass Spectrometry Method for Analysis of Urinary Conjugated Metanephrine and Normetanephrine for Screening of Pheochromocytoma Clin. Chem., March 1, 2002; 48(3): 533 - 539. [Abstract] [Full Text] [PDF]
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D. K. Crockett, E. L. Frank, and W. L. Roberts Rapid Analysis of Metanephrine and Normetanephrine in Urine by Gas Chromatography-Mass Spectrometry Clin. Chem., February 1, 2002; 48(2): 332 - 337. [Abstract] [Full Text] [PDF]
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G. Eisenhofer Free or Total Metanephrines for Diagnosis of Pheochromocytoma: What Is the Difference? Clin. Chem., June 1, 2001; 47(6): 988 - 989. [Full Text] [PDF]
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