Clinical Endocrinology

Plasma-free vs deconjugated metanephrines for diagnosis of phaeochromocytoma

Authors

  • Christina Pamporaki,

    Corresponding author
    1. Department of Medicine ΙΙI, University Hospital Carl Gustav Carus at the TU Dresden, Dresden, The Netherlands
    • Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus at the TU Dresden, Dresden, Germany
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  • Roland Därr,

    1. Department of Medicine ΙΙI, University Hospital Carl Gustav Carus at the TU Dresden, Dresden, The Netherlands
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  • Michael Bursztyn,

    1. Department of Medicine ΙΙI, University Hospital Carl Gustav Carus at the TU Dresden, Dresden, The Netherlands
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  • Stephan Glöckner,

    1. Department of Medicine ΙΙI, University Hospital Carl Gustav Carus at the TU Dresden, Dresden, The Netherlands
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  • Stefan R. Bornstein,

    1. Department of Medicine ΙΙI, University Hospital Carl Gustav Carus at the TU Dresden, Dresden, The Netherlands
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  • Jacques W. M. Lenders,

    1. Department of Medicine ΙΙI, University Hospital Carl Gustav Carus at the TU Dresden, Dresden, The Netherlands
    2. Department of Internal Medicine, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
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  • Karel Pacak,

    1. Program in Reproductive and Adult Endocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
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  • Axel Krinner,

    1. Faculty of Medicine, Institute for Medical Informatics and Biometry, Carl Gustav Carus, Dresden University of Technology, Dresden, Germany
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  • Graeme Eisenhofer

    1. Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus at the TU Dresden, Dresden, Germany
    2. Department of Medicine ΙΙI, University Hospital Carl Gustav Carus at the TU Dresden, Dresden, The Netherlands
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Correspondence: Pamporaki Christina, Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus at the TU Dresden Fetscherstraße 74, D-01307 Dresden, Germany.Tel.: 0049 351 458 14578; Fax: 0049 351 458 7346; E-mail: Christina.Pamporaki@uniklinikum-dresden.de

Summary

Background

The diagnosis of phaeochromocytoma is commonly performed by the measurements of plasma-free normetanephrine and metanephrine. Plasma-deconjugated normetanephrine and metanephrine have been proposed as alternative, equivalent, but easier to measure biomarkers.

Objective

The aim of this study was to compare the diagnostic performance of plasma-free vs deconjugated normetanephrine and metanephrine in patients tested for phaeochromocytoma.

Methods

The study population included a reference group of 262 normotensive and hypertensive volunteers, 198 patients with phaeochromocytoma and 528 patients initially suspected of having the tumour, but with negative investigations after at least 2 years of follow-up. Measurements were performed using liquid chromatography with electrochemical detection.

Results

Plasma concentrations of free normetanephrine were 17-fold higher in patients with phaeochromocytoma than in the reference population, a 72% larger (P < 0·001) difference than that for the 10-fold higher levels of plasma-deconjugated normetanephrine. In contrast, relative increases in plasma concentrations of free and deconjugated metanephrine were similar. Using upper cut-offs established in the reference population, measurements of plasma-free metabolites provided superior diagnostic performance than deconjugated metabolites according to measures of both sensitivity (97% vs 92%, P = 0·002) and specificity (93% vs 89%, P = 0·012). The area under the receiver operating characteristic curve for the free metabolites was larger than that for the deconjugated metabolites (0·986 vs 0·965, P < 0·001).

Conclusion

Measurements of plasma-free normetanephrine and metanephrine are superior to the deconjugated metabolites for diagnosis of phaeochromocytoma.

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