At a Glance
Why Get Tested?
To screen for the presence of sickle cell trait or to confirm the presence of sickle cell disease
When to Get Tested?
If you are of Afro-Carribean descent to determine if you carry one or both genes for sickle cell disease and for antenatal screening. There are other ethnic minorities in whom the sickle gene is found and should be tested if index of clinical suspicion is high.
A blood sample taken from a vein in the arm. In children, a blood sample from a finger-prick or heel-prick
Test Preparation Needed?
None; however, if this test is used for diagnosis, the sample should not be taken after a recent blood transfusion
The Test Sample
What is being tested?
Blood is tested for the presence of Haemoglobin S (HbS), which is a genetic variant of the protein haemoglobin. Haemoglobin is found inside red blood cells (RBCs) and is responsible for carrying oxygen from the lungs to all of the tissues and organs of the body. Normally haemoglobin exists in various forms (Haemoglobin A, Haemoglobin A2, and Haemoglobin F) that are present in different amounts. One genetically abnormal haemoglobin is known as HbS, which causes the RBC to change shape and affects its ability to carry oxygen. In sickle cell disease, one abnormal HbS gene is inherited from each of the parents. The RBC in these individuals change shape, thus affecting the ability of the red cells to carry oxygen.
How is the sample collected for testing?
In young children a finger-prick or heel-prick is performed to obtain a few drops of blood. In adults, a blood sample is obtained from a vein.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed; however, testing for diagnosis should not be performed after a recent blood transfusion.
Ask a Laboratory Scientist
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.