Measurement of plasma free metanephrines using on-line solid phase extraction high performance liquid chromatography tandem mass spectrometry.

Pheochromocytoma is a rare, catecholamine-producing tumour of the adrenal medulla and its presence must be considered in many patients with hypertension, the latter representing a quarter of the adult population in Western countries. The clinical hallmark is sustained or intermittent hypertension often associated with paraoxysmal symptoms however, pheochromocytoma should also be considered if a patient presents with labile hypertension and hypertension resistant to anti-hypertensive therapies.