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Porphyrins - blood |
| Definition: |
| This test measures total red blood cell porphyrins. Porphyrins are pigments found in both animal and plant life. They are involved in the formation of many important substances in the body including hemoglobin which carries oxygen in the blood. Coproporphyrin, protoporphyrin, and uroporphyrin are three porphyrins related to red blood cells that can normally be measured in small amount in the human blood stream. Protoporphyrin is normally found in highest quantity and thus this test is occasionally known as the PROTO test. Additional tests must be performed to know the levels of specific porphyrins. |
| Alternative Names: |
| Uroporphyrin levels; Protoporphyrin levels; Porphyrins - total; Coproporphyrin levels |
| How the test is performed: |
| Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding. The sample is then placed in ice and taken immediately to the laboratory. |
| How to prepare for the test: |
| Fasting for 12 to 14 hours prior to this test is required. You may drink water right before the test. If your child is to have this test performed it may be helpful to explain how the test will feel, and even practice or demonstrate on a doll. The more familiar your child is with what will happen to them, and the purpose for the procedure, the less anxiety they will feel. |
| How the test will feel: |
| When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. |
| Why the test is performed: |
| This test is used to diagnose porphyrin disorders involving red blood cells. In combination with other tests, this test is useful for diagnosing disorders such as lead poisoning and some neurologic and skin disorders. |
| Normal Values: |
This test specifically measures total porphyrin levels, but reference values (i.e., range of values seen in a group of "healthy" people) for the individual components are also included:
Note: mcg/dl = micrograms per deciliter It is important to recognize that these reference ranges will vary between different laboratories depending upon the way the test is performed. Individual results must therefore be interoperated accordingly. |
| What abnormal results mean: |
Increased levels of coproporphyrins may indicate:
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| What the risks are: |
| Risks associated with venipuncture are slight: |
| Special considerations: |
| Failure to comply with dietary restrictions prior to the test may alter and invalidate test results. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. |
Reviewed By: Michael C. Milone, M.D., Ph.D., Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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