Parkinson's disease: The effect of L-dopa therapy on urinary free catecholamines
The usual methods are measurement of urinary free catecholamines
and its metabolites VMA and MNs in a 24-hour urine sample.
Of the 95 patients with MAD or NMT over the upper reference limit, 30 patients had no further follow-up because negative results were obtained for repeat testing of either urinary fractionated metanephrines or urinary free catecholamines
. Imaging analysis was performed on 28 patients (abdominal computerized tomographic scan or magnetic resonance imaging; 1 patient had abdominal ultrasound only), with resulting diagnoses of pheochromocytoma in 14 patients; other pathologies (metastatic carcinoma, adrenal hemorrhage, adrenal myelolipoma, pelvic fibromatosis, or neuromyotonia, which was diagnosed after neurophysiology tests) in 9 patients, and no atypical findings in 5 patients.
The measurement of plasma MN and NMN has been shown to be more clinically sensitive than urinary free catecholamines
and metanephrines for the detection of pheochromocytoma (8-11).
Recently, the measurement of plasma free metanephrine and free normetanephrine has been advocated as being more clinically sensitive than urinary free catecholamines and metanephrines (tM plus tNM together) (6).
The aim of this study was to determine whether drugs commonly prescribed to subjects with symptoms of pheochromocytoma interfere with the measurement of urinary free catecholamines and total metanephrines by these new immunoassays.
The automation of such techniques using automated sequential trace enrichment of dialysates (ASTED)  has been applied successfully to the assay of urinary free catecholamines (2).
(13.) Urinary free catecholamines. Gilson Asted applications guide, 2nd ed.
In the present experiments, urinary free catecholamines
were assayed using a modification of a method described previously (7).