A sickle cell test looks for the presence or absence of abnormal hemoglobin in the blood that causes sickle cell anemia.

Blood is drawn from a vein on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an airtight vial or a syringe. During the procedure, the band is removed to restore blood flow. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

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.

This test is done to tell if you have abnormal hemoglobin that causes sickle cell disease and sickle cell trait.

In sickle cell disease, a person has two abnormal hemoglobin S genes.

A person with sickle cell trait has only one of the problem hemoglobin S genes and no symptoms, or only mild ones.

However, this test does not tell the difference between these two conditions. Another test called hemoglobin electrophoresis is needed to do so.

A negative test result is normal.

• Sickle cell trait
• Sickle cell anemia

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

Iron deficiency or blood transfusions within the past 3 months can cause a false negative result.

Hoffman R, Benz Jr. EJ, Shattil SJ, et al., eds. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingston; 2005:627-29.

McPherson RA and Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: WB Saunders; 2007:522.