A comparison of plasma-free metanephrines with plasma catecholamines in the investigation of suspected phaeochromocytoma.
J Hypertens. 2011 Oct 13;
Authors: Lee GR, Johnston PC, Atkinson AB, McKillop D, Auld P, Hunter SJ
OBJECTIVE: To compare the diagnostic performance of plasma metanephrines by ELISA and plasma catecholamine measurements by HPLC in patients selected for clonidine suppression testing. METHODS: Plasma catecholamines adrenaline (ADR) and noradrenaline (NOR) were measured by HPLC and metanephrine with normetanephrine (NMN) by ELISA (n?=?67). The diagnostic performance of metanephrines was determined by receiver operating characteristic (ROC) curve analysis. RESULTS: Phaeochromocytoma was confirmed by histological analysis in 14 patients and excluded in 53 patients by a negative clonidine suppression test (CST), abdominal computerized tomography scan and clinical follow-up (median 2.5 years). A sensitivity and specificity of 100 and 96%, respectively, was obtained by using our current CST diagnostic criteria for ADR and NOR values. ROC curve analysis revealed optimum sensitivity and specificity for plasma-free metanephrines using a threshold of 784?pmol/l at baseline and 663?pmol/l at 180?min. Baseline measurements of metanephrine with NMN showed 100% sensitivity and 98% specificity, as assessed by ROC curve analysis-derived criteria or when evaluated against published decision thresholds. A sensitivity and specificity of 100% was obtained for the combined measurements of metanephrine with NMN at 180?min. CONCLUSION: Plasma metanephrines (metanephrine with NMN) were equally effective as plasma catecholamines during CST. This study supports the use of measuring plasma metanephrines by ELISA as a less labour-intensive and equally effective biochemical test for phaeochromocytoma in patients with a high clinical suspicion. There was still overlap between groups with and without phaeochromocytoma at baseline under controlled conditions and clinically some patients still need to undergo clonidine suppression testing.
PMID: 22002333 [PubMed - as supplied by publisher]