Download Lab (11) VMA

• Generally, unfortunately most of the
hormones are present in blood in such small
amounts that their measurement is very
difficult.
• Some of hormones or their metabolites are
excreted in the urine and in many instances
their concentration in urine is much greater
than in blood. Since it is much easier to
obtain a few hundred milliliters of urine,
than, say,20 ml of blood, some hormone
analysis may be done with urine. Since the
hormone excretion rate may vary during the
day. The use of a 24 hour urine specimen
gives more accurate results.
• Not all hormones are excreted in the urine in
appreciable amounts, those of lower molecular
weight, e.g. the steroids, are more likely to be
found in the urine in measurable amounts than
are larger molecules such as the pituitary
hormones.
• In some instances the hormone itself may not be
excreted in the urine in large quantities, but
various metabolites of the hormone may be
found. The measurement of these metabolites
sometimes gives satisfactory estimate of the
amount of original hormone present in the blood.
Vanillylmandelic Acid, 24 hr urine.
• Vanillylmandelic acid (VMA) is one of
the metabolites of the catecholamines
epinephrine (adrenaline) and
norepinephrine. This test measures
the amount of VMA that is excreted
into the urine, typically over a 24-hour
period,
• Screening children for catecholamine-secreting
tumors.
• Supporting a diagnosis of neuroblastoma
• Monitoring patients with a treated neuroblastoma
• The measurement of urinary metanephrines plus
VMA have been suggested as the best screening
procedure for the detection of pheochromocytomas.
• VMA is usually present in the urine in small
fluctuating amounts that only increase
appreciably during and shortly after the body is
exposed to a stressor. (24 hr is the best)
• Neuroblastomas, pheochromocytomas, and
other neuroendocrine tumors, however, can
produce large amounts of catecholamines,
resulting in greatly increased concentrations of
the hormones and their metabolites.
• The hormone releases can cause
persistent hypertension, severe headaches,
palpitations, sweating, nausea, anxiety, and
tingling in the extremities.
 Patient preparation:
• Patients should avoid for 72 hours prior to collection
salicylates, caffeine, phenothiazine and antihypertension
agents. Also coffee, tea, chocolate, fruit (especially
bananas and any vanilla containing substances).
• Collect 24-hour urine. Refrigerate 24-hour specimens
during collection.
•
Storage/Transport Temperature Refrigerated.
• Unacceptable Conditions: Specimen types other than
urine.
• Stability Ambient: Unacceptable; Refrigerated: 1 week;
Frozen: 2 weeks
• Preferred Specimen(s) : 10 mL of a 24-hour urine collected
with 25 mL 6N HCl, submitted in a leak-proof urine
container
• Minimum Volume : 5 mL
• Alternative Specimen(s) : Unpreserved 24-hour urine with
pH <6
• Collection Instructions
• 10 mL urine: pH adjusted to < 3.0, using 6N HCl. Urine
without preservative is acceptable if pH is below 6 and
the sample is shipped frozen.
• Transport Temperature: -Preserved: Room temperature
-Unpreserved: Frozen
• Specimen Stability: Room temperature: 10 days
Refrigerated: 14 days
Frozen: 1 year
• Reject Criteria: pH >3.0 Received unfrozen
• Methodology
High Performance Liquid Chromatography (HPLC)
• Clinical Significance: Urinary vanillylmandelic acid
is useful in diagnosing neuroblastoma, one of the
most common tumors in the pediatric population
Phosphate buffer
NACL
NACL
K2Co3
MP Na
MS Na