Porphyria Educational Services
PORPHYRIA EDUCATIONAL SERVICES BULLETIN
Vol. 1 No. 51
December 12, 1999
FOCUS: PORPHYRIN URINE TEST
The Porphyrin Urine Tests is a test that measures the level
of porphyrins
in urine.
An alternative name for this test is The Uropoprhyrin Test.
The test is performed by the collection of a urine for a 24-hour
period.
The test must be ordered by a physician.
The ordering physician will instruct you, if necessary, to
discontinue
drugs that may interfere with the test.
Be sure that the proper preservative has been added to the
collection jug
before leaving your doctor's office. Many a porphyrin urine test
has been
compromised because of the wrong perservative being used or lack
of a
preservative.
On day 1, urinate into the toilet upon arising in the morning.
Collect all subsequent urine (in a special container) for the
next 24-hours.
On day 2, urinate into the container in the morning upon arising.
Always cap the container.
Always void into a special "hat" which fits into the
average toilet seat.
Do not let the voided urine sit in the hat. Pour it
immediately
into the collection jug.
Try to void with no direct light as exposure of urine to
light will
diminish the number of porphyrin, and the higher number of
porphyrin
in the urine, is what is needed for an accurate test assay.
Keep it in the refrigerator or a cool place during the collection
period.
Ideally the temperature should run between 36-40 degrees, that of
the standard refrigerator setting.
Always be sure that the container is marked with your name, the
date,
the time of completion, and return it as instructed.
Do not let it sit out in room temperatures or in bright light.
Be sure the receptionist at the lab takes it to the proper
storage
in the lab immediately.
There are no risks in performing this test.
The reason that this test is performed is because of a high
degree of
suspicion that the patient may have porphyria.
The most important function of porphyrins is as components of
heme.
Heme is made from iron + protoporphyrin.
Hemoglobin is made up of four globin proteins + 4 heme groups.
Oxygen binds to the iron in the heme molecules.
Various kinds of porphyrins exist with the same basic structure.
However the various kinds of porphyrins have slightly
different chemical
appearance.
The major biochemical pathway includes conversions from
porphyrins to delta-ALA, then to PBG, then uroporphyrin,
then coproporphyrin, then protoporphyrin, and finally into the
end product,
heme.
Each step requires the presence of an enzyme. If any of the
enzymes
are deficient (because of a genetic disease or inhibition by a
toxic
substance), a type of porphyria results.
Normal values for porphyria urine tests are as follows:
random urine: negative test
24-hour urine: 50 to 300 mg per 24-hours
Note: mg = milligrams
Cost
Before you undertake this porphyrin urine test you must determine
whether you have taken any drugs which can affect test
measurements.
These drugs include aminosalicylic acid, barbiturates, chloral
hydrate,
chlorpropamide, ethyl alcohol, griseofulvin, morphine, oral
contraceptives,
phenazopyridine, procaine, and sulfonamides.
Abnormal tests results which result in increased levels of
urinary
PBG may indicate porphyria (several types), hepatic carcinoma (liver
cancer),
hepatitis or lead poisoning .
All too often porphyrin tests must be repeated a number of times.
Timing is important for many of the tests. The best time to test
is
at the onset of an acute attack and before glucose infusion has
been
given.