Porphyria Educational Services
PORPHYRIA EDUCATIONAL SERVICES BULLETIN
Vo. 1 No. 53 December 26, 1999
FOCUS: PBG Urine testing
The PBG Urine test is a test that measures the amount
of porphobilinogen in the urine.
Another name for the test is the PHB test.
The test of completed by collecting a 24-hour urine sample.
The test must be ordered by your physician.
Your physician will instruct you as to what drugs you may have to
discontinue because some drugs may interfere with the test results.
Before you leave the physician's office, be sure that the collection
jug has the correct preservative within the jug.
On day 1, urinate into the toilet upon arising in the morning.
Collect all subsequent urine in a special container called a "hat"
for the next 24-hours.
But sure to try and void in as limited of light as possible.
Exposure of the urine to light will diminish the total porphyrins
and the object of the test is to have as high as possible count of
porphyrins. Also exposure to air will diminish the porphyrins and therefore
you should never let the voided urine stand in the hat, but immediately
On day 2, urinate into the "hat" and immediately pout into the containe
in the morning upon arising.
Be sure that the cap is on the container at all times.
Keep it in the refrigerator or a cool place during the collection period.
Be sure that the collection jug is labeled with your name, the date,
the time of completion. Then return the collection jug i as instructed
by your physician.
Following the directions of your phyrisician immediately deliver the
collection jug. Be sure that it is refrigerator upon receipt.
The test may is performed when porphyria or another disorder
associated with abnormal PBG level is suspected.
PBG is a substance (enzyme) used by the body to synthesize
porphyrins (nitrogen containing organisms).
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,
but with 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.
The following are the normal values for the PBG
24-hour urine test.
: 1.5 to 2 mg (milligrams) per 24-hours
Many drugs can affect the results of the PBG 24 urine test.
Drugs that can affect test measurements include aminosalicylic acid,
barbiturates, chloral hydrate, chlorpropamide, ethyl alcohol,
griseofulvin, morphine, oral contraceptives, phenazopyridine,
procaine, and sulfonamides.
Abnormal increased levels of urinary PBG may indicate several types of
In addition elevated PBG may indicate hepatic carcinoma (liver cancer) ,
hepatitis, and lead poisoning.