Porphobilinogen (PBG) is one of a class of chemicals in the body called porphyrins. It is metabolized to heme, which is the iron containing portion of hemoglobin, which carries oxygen in the blood. When genetic defects are present, the porphyrins can not be metabolized and can accumulate in the blood causing toxicity. This disorder is called porphyria. The porphyrins are excreted in the urine, therefore testing for PBG in the urine can aid in the diagnosis of certain porphyrias.
The most common porphyrias are acute intermittent porphyria (AIP) and porphyria cutanea tarda (PCT). Urinary PBG is the most important screening tool in this disorder. Symptoms of the disease include discolored urine, abdominal pain, and often mental or neurologic symptoms if severe. Confirmatory testing for porphyria should include genetic testing if a family mutation is known or suspected. Although a diagnostic tool in porphyrias, increased urinary PBG can also be seen in liver disease such as cancer or hepatitis. Increased levels can also be seen in lead or other heavy metal poisoning, which makes urinary PBG an important part of occupational or industrial exposure screens.
Porphobilinogen urine testing is performed on a urine sample. Additional tests may include Delta (5)-Aminolevulinic Acid, Fecal Porphyrins, Blood lead levels, and Urobilinogen Urine.
Reference ranges and specimen collection vary from test method and laboratories performing this test. To properly evaluate your test results, consult with the ordering physician or healthcare provider. If you would like to learn more about testing for Porphobilinogen click here for further information or you can research one of the references listed below.
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Revision: Stig Thunell MP. (2008, August). Acute and Cutaneous Porphyrias. Retrieved October 9, 2010, from Merck Manuals Online Library: www.merck.com