Endocrine Abstracts

Background: Phaeochromocytoma and paraganglioma (PPGLs) are rare neuroendocrine tumours arising from the adrenal medulla and paraganglia. Biochemical assessment relies on demonstrating elevated concentrations of catecholamines and their metabolites. Analytical methods for catecholamine and metanephrine measurement vary in sensitivity and specificity. We reviewed our biochemical work-up in order to optimise patient diagnosis.

Methods: This retrospective audit reviewed adult patients in whom simultaneous plasma catecholamine and metanephrine measurements were available from 2013 to 2015. Catecholamines and metanephrines were analysed by high-performance liquid-chromatography with electrochemical detection and liquid chromatography-tandem mass spectrometry, respectively. Samples (catecholamines: lithium heparin with stabilisation solution and metanephrines: EDTA) were collected using established protocols. Hospital IT systems were used to obtain relevant information (investigations, multi-disciplinary meeting (MDM) outcomes and management).

Results: In total, 110 patients with paired catecholamine/metanephrine measurements had MDM review. Of these, 28 had elevated catecholamines with normal metanephrines and one elevated metanephrines but normal catecholamines. Forty-four (17M) patients aged 60 (47–68) [median(IQR)] years had histological diagnosis (23 phaeochromocytoma, 2 paraganglioma, 8 post-op PPGLs and 11 benign/other lesions). In those without histology, MDM ruled out PPGLs in 18 with elevated catecholamines but normal metanephrines. In histologically-confirmed disease, three benign lesions, two adrenocortical carcinoma and one low-grade PPGL had elevated catecholamines but normal metanephrines, along with three PPGL under follow-up. One PPGL was biochemically silent. In three samples catecholamines couldn’t be quantified due to analytical interference. PPGLs had higher catecholamines and metanephrines vs non-PPGLs: adrenaline 0.45 (0.17–1.38) vs 0.20 (0.11–0.24) [ref<0.45 nmol/l); noradrenaline 11.24 (3.46–16.42) vs 1.94 (1.68–3.46) [0.00–2.50 nmol/l]; metadrenaline 305 (113–2120) [80–510 pmol/l] vs 117(81–232) and normetadrenaline 5669 (1433–20,329) vs 277(208–378) [120–1180 pmol/l] (all P<0.05)]. Sensitivity, specificity, PPV and NPV for catecholamines vs. metanephrines were; 96/92, 61/100, 77/100 and 92/90, respectively.

Conclusions: Plasma metanephrines are superior to catecholamines due to better specificity, simpler sample collection and minimal analytical interference. The MDM approach is critical in biochemical assessment of PPGLs.