We have compared platelet and plasma
catecholamines (radioenzymatic assay with
catechol-O-methyl
transferase) and urinary metanephrines (high performance liquid chromatography) in 16 patients with phaeochromocytoma, 12 essential hypertensives, and 15 normotensive volunteers. Hypertensive patients with or without phaeochromocytoma had labile or paroxysmal
hypertension with normal or borderline blood pressures between paroxysms.
Catecholamine concentrations in platelets and plasma did not differ in essential hypertensives and controls, but were higher in patients with phaeochromocytoma than in subjects without tumour, with values overlapping between groups.
Metanephrine excretion was markedly higher in phaeochromocytoma than in
essential hypertension, with no intergroup overlap. Platelet
adrenaline plus
noradrenaline content was highly correlated to urinary metanephrines (r' = 0.830, n = 28 p less than 0.01). Using as a cut-off point the highest values measured in essential hypertensives, the sensitivity of each measurement was 1.00 for metanephrines, 0.87 for platelet
catecholamines and 0.50 or less for plasma
catecholamines. Measurement of platelet
catecholamine content is a sensitive test and an appropriate alternative to
metanephrine measurement in the difficult cases of suspected phaeochromocytoma with intermittent
hypertension.