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Porphyrins - urine
DefinitionThis is a test that measures the level of porphyrins in urine.
How the test is performedA 24-hour urine sample is needed. The health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test.
Thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with adhesive on one end), and place it on your infant. For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia. Place a diaper over the infant (bag and all). The infant should be checked frequently and the bag changed after the infant has urinated into the bag. For active infants, this procedure may take a couple of attempts -- lively infants can displace the bag, causing an inability to obtain the specimen. The urine is drained into the container for transport to the laboratory.
Deliver it to the laboratory or your health care provider as soon as possible upon completion.
How to prepare for the testThe health care provider may advise you to discontinue drugs that can affect the test. (See "Special considerations.")
If the collection is being taken from an infant, a couple of extra collection bags may be necessary.
How the test will feelThe test will feel the same as normal urination.
Why the test is performed
This test is most often performed when porphyria or other disorders that can cause abnormal urine porphyrins is suspected.
Heme production involves biochemical conversion of porphyrins into delta-ALA , then to PBG , then uroporphyrin, then coproporphyrin, then protoporphyrin, and finally into the end product -- heme.
Each of these steps requires the presence of a specific enzyme . If any of the enzymes are deficient (because of a genetic disease or interference by a toxic substance), the intermediate substances build up, and a type of porphyria results.
What abnormal results meanIncreased levels of urinary PBG may indicate:
In specific types of porphyria, levels of ALA, uroporphyrin, and coproporphyrin may also be higher than normal.
What the risks areThere are no risks.
Special considerationsDrugs that can affect test measurements include aminosalicylic acid, birth control pills, barbiturates, chloral hydrate, chlorpropamide, ethyl alcohol, griseofulvin, morphine, phenazopyridine, procaine, and sulfonamides.
Update Date: 6/1/2003Marcia S. Brose, M.D., Ph.D., Division of Hematology/Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT