Vanillylmandelic acid (VMA) and/or homovanillic acid (HVA) concentrations are elevated in over 90% of patients with neuroblastoma; both tests should be performed.
A positive test could be due to a genetic or nongenetic condition. Additional confirmatory testing is required.
A normal result does not exclude the presence of a catecholamine-secreting tumor.
Elevated HVA values are suggestive of a deficiency of dopamine beta-hydrolase, a neuroblastoma, a pheochromocytoma, or may reflect administration of L-dopa.
Decreased urinary HVA values may suggest monoamine oxidase-A deficiency.