Porphobilinogen (PBG) is one of several types of porphyrins found in your body. Normally, your body breaks down porphyrins into heme, an important part of hemoglobin. Most of the time, porphyrins usually leave your body through urine or stools. If this process does not take place, porphyrins such as PBG can build up in your body.
This article describes the test to measure the amount of PBG in a urine sample.
How the Test is Performed
A 24-hour urine sample is needed. The health care provider will tell you if you need to stop taking any of your medicines.
On day 1, urinate into the toilet when you get up in the morning.
Afterwards, collect all urine in a special container for the next 24 hours.
On day 2, urinate into the container when you get up in the morning.
Cap the container. Keep it in the refrigerator or a cool place during the collection period.
Label the container with your name, the date, the time of completion, and return it as instructed.
For an infant, thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on the 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. Diaper as usual over the secured bag.
This procedure may take a few tries. An active infant can displace the bag, causing the urine to leak into the diaper. The infant should be checked often. The bag changed after the infant has urinated into it.The urine is then drained into the collection container. Take the sample to the lab or your health care provider as soon as possible after the test is done.
How to Prepare for the Test
Your doctor may tell you to stop taking medicines that might change the test results. test results.
Drugs that can affect the test include:
Birth control pills
Never stop taking any medicine without first talking to your doctor.
How the Test will Feel
This test involves only normal urination, and there is no discomfort.
Why the Test is Performed
This test may be done if the health care provider suspects porphyria or another disorder associated with an abnormal porphobilinogen (PBG) level.
For a random urine sample, a negative test result is considered normal.
If the test is done on a 24-hour urine sample, the normal value is less than 4 milligrams per 24 hours.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What Abnormal Results Mean
Increased levels of PBG in the urine may be due to:
Anderson K. The porphyrias. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 217.
Fuller SJ, Wiley JS. Heme biosynthesis and its disorders. In: Hoffman R, Benz EJ Jr, Silberstein LE, Heslop HE, Weitz JI, eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, PA: Saunders Elsevier; 2012:chap 36.
Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.