Porphyria Educational Services
PORPHYRIA EDUCATIONAL BULLETIN Vol.1 No. 6
Testing for Porphyria
24 Hour Urine Testing Infomation
Test only when you are BEGINNING an attack.
Start the testing BEFORE you begin your glucose IV or carbo-loading.
Why? Because carbs kill/or/stop the production of porphyrins
it is the over production of porphyrins in the liver that cause an attack!
Have a lab container on hand BEFORE you get an attack.
The lab container must be LIGHT TIGHT [Be sure that no light can get to the urine.]
A heavy plastic 1 1/2 gallon container is the preferred container.
*Brown glass will not keep out light, and runs the risk of
breakage during handling.
**Metal containers will render the testing invalid.
The lab container must have the PROPER / CORRECT PRESERVATIVE.
*The preservative depends on the Protocol by the Lab to which
is being sent. Be sure that your doctor looks up the information and then
YOU doublecheck with th lab to be sure it is the CORRECT preservative.
[A wrong preservative can render useless your whole 24 hr effort].
*The standard is usually Sodium Carbonate. 5gm
For women a "hat" is most necessary along with a
funnel for pouring
the urine into the container. Males may go direct into the "neck" container
if using a collection container that attaches or can be poured directly in the
lab container from the "neck" container. However remember not to come
into bodily contact with the preservative in the container.
VOID in the dark.
Immediately close the lid.
Immediately refrigerate the container at 40
degrees [standard setting
for most refrigertors. Do not freeze!].
*As an added precaution I undid light bulb in refrigerator.
*In addition I learned to wrap the plastic lab container in
tinfoil to be
sure no light could leak.
Repeat this until your 24 hours is up.
Return to lab [if you dare trust their timeliness] or take
directly to FedEx
and have a tracker on the container. FedEx is very good about packing
the container in dry ice and a Coleman type cooler chest.
The tracker will tell you exactly where it is and if it was
held up anyway
along the way. I was paranoid enough to even call the lab to be sure it
arrived, and pushy enough to ask them if they had started the assay!!!!
Things like this after a number of causalities resulting in no
dx makes a
person go from passive to assertive!
The main object of this test is to have as HIGH
as possible. [Numbers are everything and some porph doctors will not even consider
then unless they are 20x normal level.
PORPHYRIA DIAGNOSTIC TESTING
There is not just one test for porphyria.
In fact there are many laboratory tests available for the different types of porphyria.
For the clinician it is often difficult to decide which tests
should be used in trying
to obtain a diagnosis.
Often a primary care physician will run just a few tests at a
time because of
concern for the expewnse of such testing, and also being hopeful that starting
with the simple tests, will rule in or rule out a diagnosis at the beginning.
Many of these tests are expensive. The test results are most often difficult to interpret.
Then there is the factor of the specific tests being specific or being sensitive.
The tests vary in sensitivity and specificity.
If a test is sensitive, it is unlikely to be falsely negative.
This means that the test will fail to diagnose porphyria in a
patient who has the disease.
On the other hand, if a test is specific, it is unlikely to be falsely positive. A false positive test
will diagnose porphyria in a patient who does not have porphyria.
Certain tests are both sensitive and specific in patients who
that are suggestive of porphyria.
When abdominal and neurological symptoms suggest an acute
the best screening tests are urinary ALA and PBG
ALA is the abbreviation for delta aminolevulinic acic.
PBG is the abbreviation for porphobilinogen.
When there are cutaneous symptoms that suggest porphyria, the
best screening test is a
plasma porphyrin determination. If one of these screening tests is abnormal, more
extensive testing, including urinary, fecal and red blood cell porphyrins, are then indicated.
Urinary, fecal, and red blood cell porphyrin measurements are not very
useful for initial screening, because they lack either sensitivity or specificity and, therefore,
are often difficult to interpret. Measurement of heme biosynthetic enzymes in red blood cells or
lymphocytes is not appropriate for screening, unless it is part of a family study that is done
after someone in the family is already known to have a particular enzyme deficiency.
It is advisable to have testing performed by a laboratory that has expertise in the
clinical aspects of porphyria and can provide a valid interpretation of the test results.
If testing has been performed in laboratories other than porphyria
laboratories, consultation with a porphyria expert is advised before
a final diagnosis of acute porphyrias is accepted.