First step in diagnosis in phaeochromocytoma is

The first step in the diagnosis of a phaeochromocytoma is the confirmation of excessive catecholamine levels in the patient either by the measurement of adrenaline and noradrenaline breakdown products, metanephrine and normetanephrine level, in a 12 or 24-hour urine collection.The biochemical diagnosis is then followed by localisation of the phaeochromocytoma. MRI is preferred because contrast media used for CT scans can provoke paroxysms.123I-MIBG (metaiodobenzylguanidine) single-photon emission computed tomography (SPECT) will identify about 90% of primary tumours and is essential for the detection of multiple extra-adrenal tumours and metastasesRef: Bailey and Love 27e pg: 845