Sickle cell test
Definition
A sickle cell test looks for the presence or absence of abnormal hemoglobin in the blood that causes sickle cell anemia.
Alternative Names
How the Test is Performed
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.
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 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.
Normal Results
A negative test result is normal.
What Abnormal Results Mean
- Sickle cell trait
- Sickle cell anemia
Risks
- 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
Considerations
Iron deficiency or blood transfusions within the past 3 months can cause a false negative result.
References
Saunthararajah Y, Vichinsky EP, Embury SH. Sickle cell disease. In: Hoffman R, Benz Jr. EJ, Shattil SJ, Furie B, Cohen HJ, eds. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingston;2005;chap 37.
Reviewed By: James R. Mason, MD, Oncologist, Director, Blood and Marrow Transplantation Program and Stem Cell Processing Lab, Scripps Clinic, Torrey Pines, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
