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  • Title: The value of immunoassays for metanephrines in the biochemical diagnosis of pheochromocytomas.
    Author: Unger N, Deutschbein T, Walz MK, Mann K, Petersenn S.
    Journal: Horm Metab Res; 2009 Sep; 41(9):676-9. PubMed ID: 19557670.
    Abstract:
    An undiagnosed pheochromocytoma may result in life-threatening consequences. The diagnosis of pheochromocytoma is based on the overproduction of catecholamines. Highly sensitive biochemical assays are essential to avoid false-negative results. Determinations of 24-h urinary epinephrine and norepinephrine levels are established diagnostic tools. However, they may be falsely negative in patients with a biochemically-silent or periodically-secreting pheochromocytoma. Metanephrines, which are metabolites of catecholamines, have been suggested as an alternative diagnostic tool. Urinary metanephrines are determined by high-pressure liquid chromatography (HPLC) in an increasing number of laboratories, whereas plasma metanephrines measured by HPLC are available in specialised centres only. The different HPLC methods may be cost- and time-intensive. Immunoassays such as radio- or enzyme-immunoassays may be alternative procedures. Measurement of metanephrines instead of catecholamines by either technique improved the diagnostic accuracy for the diagnosis of pheochromocytomas. Determination of plasma free metanephrines demonstrated a higher accuracy than their urinary counterparts. The use of immunoassays may be an alternative to the laborious HPLC, although the method needs to be evaluated in more detail.
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