title: Simultaneous liquid chromatography tandem mass spectrometric determination of urinary free metanephrines and catecholamines, with comparisons of free and deconjugated metabolites.
abstract: OBJECTIVE
  We introduce a novel liquid chromatographic tandem-mass spectrometric method for simultaneous measurements of urinary catecholamines and their free O-methylated metabolites, which we compare to the deconjugated metabolites.
  
  
  METHODS
  Method performance was validated for recovery, linearity, precision and accuracy, analyte stability, ion suppression and carry over. Results from 53 patients with and 138 volunteers without pheochromocytoma were compared.
  
  
  RESULTS
  Analyte recoveries ranged from 60 to 96% and intra- and inter-assay coefficients of variation from 2.7 to 13.2%. The method showed excellent linearity over 3 orders of magnitude with analytical sensitivity sufficient to measure to 1.2 nmol/L. Free O-methylated metabolites were excreted at less than 20% the rates of the deconjugated metabolites, but were easily measureable. Increases in urinary normetanephrine in pheochromocytoma patients relative to volunteers were higher for free than deconjugated metabolites and higher for both than for norepinephrine (10 vs 5.5 vs 3.7 fold increases). In contrast, relative increases in urinary free versus deconjugated metanephrine (2.7 and 3.2) and methoxytyramine (2.1 and 1.9) did not differ, but for methoxytyramine were larger than for dopamine (1.2).
  
  
  CONCLUSIONS
  Measurements of urinary catecholamines and their free O-methylated metabolites by our method provide potential advantages over urinary deconjugated metanephrines for diagnosis of pheochromocytoma.
authors: Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus at the TU Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany. Mirko.Peitzsch@uniklinikum-dresden.de
authors: Mirko
authors: M
authors: Peitzsch
authors: Daniela
authors: D
authors: Pelzel
authors: Stephan
authors: S
authors: Glöckner
authors: Aleksander
authors: A
authors: Prejbisz
authors: Martin
authors: M
authors: Fassnacht
authors: Felix
authors: F
authors: Beuschlein
authors: Andrzej
authors: A
authors: Januszewicz
authors: Gabriele
authors: G
authors: Siegert
authors: Graeme
authors: G
authors: Eisenhofer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002395:Catecholamines / Q000378:metabolism* / Q000652:urine*; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D008297:Male; D008676:Metanephrine / Q000378:metabolism* / Q000652:urine*; D008875:Middle Aged; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry; D055815:Young Adult
chemical_list: D002395:Catecholamines; D008676:Metanephrine