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Technical Briefs |
Departments of1 Internal Medicine, 2 Chemical Endocrinology, and 3 Endocrinology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands; 4 Clinical Neurocardiology Section, National Institute of Neurological Disorders and Stroke and 5 Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD;
aaddress correspondence to this author at: Department of Internal Medicine, Radboud University Nijmegen Medical Center, Geert Grooteplein, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands; fax 31-24-3541734, e-mail j.lenders{at}aig.umcn.nl
Abstract
Background: The impact of blood sampling in sitting vs supine positions on measurements of plasma metanephrines for diagnosis of pheochromocytoma is unknown.
Methods: We compared plasma concentrations of free metanephrines in samples from patients with primary hypertension obtained after supine rest with those obtained in the sitting position without preceding rest. We also assessed the effects on diagnostic test performance retrospectively in patients with and without pheochromocytoma, and we calculated cost-effectiveness for pheochromocytoma testing.
Results: Upper reference limits of plasma free metanephrines were higher in samples obtained from seated patients without preceding rest than from supine patients with preceding rest. Application of these higher upper reference limits to samples from supine patients with pheochromocytoma decreased the diagnostic sensitivity from 99% to 96%. In patients without pheochromocytoma, adjusting the plasma concentration for the effects of sitting while preserving the 99% sensitivity by use of the supine upper reference limits increased the number of false-positive test results from 9% to 25%.
Conclusions: To preserve high diagnostic sensitivity we recommend the use of upper reference limits determined from blood samples collected in the supine position. Under these conditions, negative test results for blood samples obtained with patients sitting are as effective for ruling out pheochromocytoma as negative results from samples obtained after supine rest. Repeat testing with samples obtained in the supine position offers a cost-effective approach for dealing with the increased numbers of false-positive results expected after initial sampling in the sitting position.
The following articles in journals at HighWire Press have cited this article:
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  W. H. A. de Jong, G. Eisenhofer, W. J. Post, F. A. J. Muskiet, E. G. E. de Vries, and I. P. Kema Dietary Influences on Plasma and Urinary Metanephrines: Implications for Diagnosis of Catecholamine-Producing Tumors J. Clin. Endocrinol. Metab., August 1, 2009; 94(8): 2841 - 2849. [Abstract] [Full Text] [PDF]
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 R. T Peaston and S. Ball Biochemical detection of phaeochromocytoma: why are we continuing to ignore the evidence? Ann Clin Biochem, January 1, 2008; 45(1): 6 - 10. [Abstract] [Full Text] [PDF]
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A. Algeciras-Schimnich, C. M. Preissner, W. F. Young Jr., R. J. Singh, and S. K. G. Grebe Plasma Chromogranin A or Urine Fractionated Metanephrines Follow-Up Testing Improves the Diagnostic Accuracy of Plasma Fractionated Metanephrines for Pheochromocytoma J. Clin. Endocrinol. Metab., January 1, 2008; 93(1): 91 - 95. [Abstract] [Full Text] [PDF]
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 A. Karagiannis, D. P Mikhailidis, V. G Athyros, and F. Harsoulis Pheochromocytoma: an update on genetics and management Endocr. Relat. Cancer, December 1, 2007; 14(4): 935 - 956. [Abstract] [Full Text] [PDF]
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 R. J. Singh and G. Eisenhofer High-Throughput, Automated, and Accurate Biochemical Screening for Pheochromocytoma: Are We There Yet? Clin. Chem., September 1, 2007; 53(9): 1565 - 1567. [Full Text] [PDF]
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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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