Evaluation of specific high-performance liquid-chromatographic determinations of urinary metanephrine and normetanephrine by comparison with isotope dilution mass spectrometry - (vol 38, pg 356, 2001)

A method for the determination of metanephrine (MN, also known as metadrena line), normetanephrine (NMN also known as normetadrenaline) and 3-methoxyty ramine (3-MT) in human urine using high-performance liquid chromatography f ollowed by electrochemical detection (ECD) was validated primarily by compa ring the results with those obtained by a gas chromatography-mass spectrome try (GC-MS) reference method. Correlation coefficients of 0.93, 0.94 and 0. 91 were obtained for MN, NMN and 3-MT, respectively. in a group of healthy controls consisting of 30 women and 30 men. A systematic difference was det ected only for 3-MT (-16%). Further tests of accuracy (linearity and recove ry) and precision demonstrated that the described method must be considered to be a reliable approach to assess urinary metanephrines in the diagnosis of phaeochromocytoma. At lower concentrations (MN, 248 nmol/L, NMN, 434 nm ol/L; 3-MT, 402 nmol/L), within-assay coefficients of variation were close to 5% or less (5.3, 4.6 and 2.2%, respectively) and between-assay coefficie nts of variation were 8.9, 11.2 and 12.3%, respectively, for the same low l evels. This raises the possibility that this method can also be applied to assess urinary free, unconjugated metanephrines. Sex differences were detec ted for MN and NMN excretion when expressed in nmol per 24h and nmol/mmol c reatinine, respectively, by both ECD and GC MS methods.