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Porphyrins - blood

Definition

Porphyrins are a group of chemicals that help form many important substances in the body, including hemoglobin, the protein in red blood cells that carries oxygen in the blood.

This article discusses the test to measure the total amount of porphyrins in your blood.

See also: Porphyrins - urine

Alternative Names

Protoporphyrin levels; Porphyrins - total; Coproporphyrin levels; PROTO test

How the test is performed

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

The sample is then placed in ice and taken immediately to the laboratory. Three porphyrins can normally be measured in small amounts in human blood. They are:

  • Coproporphyrin
  • Protoporphyrin (PROTO)
  • Uroporphyrin

Protoporphyrin is normally found in the highest amount. Additional tests are needed to show the levels of specific porphyrins.

How to prepare for the test

You should not eat for 12 - 14 hours before this test. You may drink water right before the test. Failure to follow these restrictions may affect the test results.

How the test will feel

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

This test is used to diagnose porphyrias, a group of rare disorders often passed down through family members.

It may also be used along with other tests to diagnose lead poisoning and certain nervous system and skin disorders.

Normal Values

This test specifically measures total porphyrin levels, but reference values (a range of values seen in a group of healthy people) for the individual components are also included:

  • Total porphyrin levels: 16 to 60 mcg/dL
  • Coproporphyrin levels: < 2 mcg/dL
  • Protoporphyrin levels: 16 to 60 mcg/dL
  • Uroporphyrin levels: < 2 mcg/dL

Note: mcg/dL = micrograms per deciliter

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Increased levels of coproporphyrins may indicate:

Increased protoporphyrin levels may indicate:

Increased uroporphyrin levels may indicate:

  • Congenital erythropoietic porphyria

What the risks are

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.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

References

Anderson KE. The porphyrias. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 229.


Review Date: 8/9/2009
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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