Porphyrins - blood

Definition

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

A test can be done measure the total amount of porphyrins in your blood.

See also:

Porphyrins - urine test

Alternative Names

How the test is performed

Blood is 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, and uroporphyrin. Protoporphyrin is normally found in highest amount, which is why this test is also known as the PROTO test. 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.

If your child is going to have this test, it may be helpful to explain how the test will feel, and even demonstrate on a doll. Explain the reason for the test. Knowing the "how and why" may reduce the anxiety your child feels.

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 rare group of disorders passed down through families.

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

It is important to recognize that these reference ranges will vary between different laboratories depending upon the way the test is performed.

What abnormal results mean

Increased levels of coproporphyrins may indicate:

• Congenital erythropoietic porphyria
• Sideroblastic anemia

Increased protoporphyrin levels may indicate:

• Infection
• Thalassemia
• Sideroblastic anemia
• Lead poisoning
• Iron deficiency anemia
• Erythropoietic anemia
• Increased erythropoiesis

Increased uroporphyrin levels may indicate:

• Congenital erythropoietic porphyria
• Erythropoietic protoporphyria

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)