vanillylmandelic acid
Last reviewed 07/2021
Phaeochromocytoma may be diagnosed from the measurement of urinary free catecholamines i.e. adrenaline, noradrenaline, or their metabolites e.g. vanyl-mandelic acid (VMA / HMMA).
Urine catecholamine measurement has a 99.5% specificity and 100% sensitivity in patients with phaeochromocytoma (1). Measurement of catecholamine metabolites e.g. VMA, has a reduced sensitivity.
At least three 24 hour urine collections are necessary as many patients with phaeochromocytoma have intermittently raised levels.
The ingestion of substances containing phenols such as coffee, bananas, and vanilla flavourings, or of drugs such as methyldopa which interfere centrally or peripherally with sympathetic function, is to be avoided in the 24 hours prior to collection.
Twice normal levels are generally considered diagnostic of phaeochromocytoma (1). Levels may be slightly elevated in essential hypertension.
Reference:
- Foo M et al (1995). Phaeochromocytoma, BJHM, 54(7), 318-22.