Porphobilinogen (PBG) Deaminase,
Erythrocyte Test
This test is
significant in evaluating most AIP patients.
However
there are 14% of AIP patients who will not have a
decrease in the PBG-D.
The test is
performed through enzymatic study and fluorometry.
Porphobilinogen (PBG) deaminase (also called
uroporphyrinogen-1-synthase and hydroxymethylbilane
synthase) is present in red cells and catalyzes the
formation of uroporphyrinogen from porphobilinogen.
In
persons genetically susceptible acute intermittent
porphyria (AIP), PBG deaminase levels are approximately
half of usual values, except in the 14% aforementioned.
. Normal levels of
erythrocyte PBG deaminase, however, do not exclude rare
abnormal forms of hepatic PBG deaminase measured activity.
Measurement of
porphobilinogen deaminase activity is of
limited use in assessing patients with latent acute
intermittent porphyria.
It is best for only those patients who are acute or
chronic.
The clinical
usefulness of PBG deaminase is limited both technically
and clinically.
Test reference
levels: Adult: 2.10-4.30 mU/g HGB.
Dr. Robert Johnson MD
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Porphyrin Red Blood Cell
Testing
Another of the
tests for porphyria is that of the porphyrin red
blood cell.
Often it is
given in conjunction with a 24 porphyrin urine test.
Other names for this tests are: uroporphyrin levels;
protoporphyrin
levels; porphyrins, total; coproporphyrin levels
Porphyrins are
pigments found in both animal and plant life.
The Nobel Laureate, Hans Fischer in 1930, called
porphyrins that which
"make the grass green, and the blood red".
Coproporphyrin,
protoporphyrin, and uroporphyrin are three
porphyrins related to red blood cells that can normally
be measured in small amount in the human blood stream.
Protoporphyrin
is normally found in highest quantity and thus this
test is occasionally known as the PROTO test.
Additional
tests must be performed to know the levels of specific
porphyrins.
The test is
undertaken by drawing blood from a vein (venipuncture).
The point of
entry is often from the inside of the elbow or the
back of the hand.
The puncture
site is cleaned with antiseptic, and a tourniquet (an
elastic band) or blood pressure cuff is placed around the
upper arm to apply pressure and restrict blood flow
through the vein.
When this is
done it causes veins below the tourniquet to
distend
(fill with blood).
A needle is
inserted into the vein, and the blood is collected in
an air-tight vial or a syringe.
Midway through
the procedure, the tourniquet is removed so that
the blood circulation cam resume. Once the
blood has been collected, the
needle is removed, and the puncture site is covered to
stop any bleeding.
The sample is then placed in ice and
taken immediately to the laboratory.
Sometimes when the
needle is inserted to draw blood, it is found that
some people will feel moderate pain. The majority of
people will feel only
a prick or stinging sensation. Afterward, there may be
some throbbing.
The test is
performed do that physicians can diagnose porphyrin
disorders involving red blood cells.
This test
specifically measures total porphyrin levels, but
reference values for the individual components are also
included:
The normal value ranges are as follows:
total porphyrin levels: 16 to 60 mcg/dl
coproporphyrin levels: < 2 mcg/dl
protoporphyrin levels: 16 to 60 mcg/dl
uroporphyrin levels: < 2 mcg/dl
Note: mcg/dl = micrograms per deciliter
It must be remembered that when you undertake this test
you must
follow the dietary restrictions. If you do not follow the
dietary
restrictions it will often alter and invalidate
test results.
When you test results show abnormal increased levels of
coproporphyrins, it may indicate congenital
erythropoietic porphyria,
as well as sideroblastic anemia.
Increased
protoporphyrin levels may indicate that the patients has
infection, thalassemia, sideroblastic anemia, lead
poisoning,
iron deficiency anemia, erythropoietic anemia , or
increased erythropoiesis.
Increased
uroporphyrin levels often indicate erythropoietic
protoporphyria. [EOO]. This test must be ordered by your
physician.
In order to
prepare for the test you must be fasting for 12 to 14
hours prior to the time of this test. You may
drink water right before
the test.
If you have
any carbohydrate intake, you will compromise your test.
Therefore you must avoid the carbohydrates during the
time
preceeding the blood draw.
Dr. Robert Johnson MD
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Fecal Matter Testing
Fecal Porphyrin Test
The patient must collect the stools over a three day period after carefully
following dietary and pharmaceutical restrictions. The patients must have been
off of most drugs for a minimum of four days and have avoided certain foods for
4 to 7 days.
The test is completed by the use of high performance liquid chromatography known
as (HPLC).
The significance of the fecal porphyrin tests is that fecal porphyrins are elevated
in disorders such as variegate porphyria [VP], hereditary coproporphyria [HCP]
and erythropoietic protoporphyria [EPP] .
Coproporphyrins can also be elevated in a variety of acquired conditions, such as
liver disease and by diet.
The stool porphyrins will be normal in acute intermittent porphyria. Reference
Interval:
Coproporphyrin: 0-45 nmol/g dry weight
Protoporphyrin: 0-150 nmol/g dry weight
Please realize that bacterial modifications of fecal porphyrins are extensive.
Dr. Robert Johnson MD
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