Sickle Cell Tests
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- Also Known As:
- Hemoglobin S
- Hb S
- Hgb S
- Formal Name:
- Hemoglobin S Evaluation

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At a Glance
Why Get Tested?
To determine if you have sickle cell trait or sickle cell disease
When To Get Tested?
Routinely as part of newborn screening; if you are in a high risk group and were born before newborn screening was mandated and want to know if you have sickle cell disease or are carrying the sickle cell trait; when you have signs and symptoms of anemia or abnormal results from a complete blood count (CBC) and your health care practitioner suspects sickle cell disease or trait
Sample Required?
A blood sample drawn from a vein in your arm or, for infants, by pricking a heel or finger
Test Preparation Needed?
None; however, if this test is used for diagnosis, the sample should not be drawn after a recent blood transfusion.
What is being tested?
Sickle cell anemia is an inherited disorder that leads to the production of an abnormal type of hemoglobin called hemoglobin S (Hb S or Hgb S). Sickle cell tests determine the presence and relative amount of hemoglobin S in a blood sample or detect mutations in the genes that produce hemoglobin to help diagnose sickle cell anemia and/or identify people with sickle cell trait.
Hemoglobin is the protein in red blood cells (RBCs) that binds to oxygen in the lungs and carries it to tissues throughout the body. Typically, hemoglobin A (Hb A, adult hemoglobin) makes up most of the hemoglobin found in normal RBCs in adults, with small amounts of hemoglobin A2 and hemoglobin F. Before babies are born, they normally produce large amounts of hemoglobin F (Hb F, fetal hemoglobin), which is then replaced by Hb A as the predominant hemoglobin shortly after birth.
Sickle cell disease is an inherited condition, passed from parents to children. Inheriting mutations in the genes that code for the production of hemoglobin can lead to abnormal types of hemoglobin (variants), such as Hb S and hemoglobin C (Hb C). Hemoglobin Cis one of the more common hemoglobin variants and may cause no symptoms or mild illness.
- Sickle cell disease and anemia—a person who inherits two abnormal gene copies (alleles), one of which is a Hb S gene, has sickle cell disease (i.e., a person who has one Hb S gene copy and one Hb C gene copy has sickle cell disease.) A person who inherits two Hb S gene copies (one from each parent; homozygous) has sickle cell anemia, the most common and serious for of sickle cell disease.
- Sickle cell trait (carrier)—a person who inherits one normal hemoglobin gene copy from one parent and a Hb S gene copy from the other parent (heterozygous) has sickle cell trait and is a sickle cell carrier. Carriers generally don’t experience signs and symptoms associate with sickle cell disease but can pass the mutation to their children.
Hb S can form crystals that change the shape of the RBC from a round disc to a characteristic sickle shape. This altered shape limits the RBC’s ability to flow smoothly throughout the blood vessels in the body, limits the hemoglobin’s ability to transport oxygen to tissues, and decreases RBC lifespan from 120 days to about 10-20 days. A person with sickle cell disease (homozygous for Hb S) can become severely anemic because the body cannot produce RBCs as fast as they are destroyed. The affected person can suffer painful episodes and a variety of complications when sickled cells become lodged in and obstruct small blood vessels.
Common Questions
View Sources
Sources Used in Current Review
Hemoglobin S, Screen, Blood Clinical Information. Mayo Clinic, Mayo Medical Laboratories. Available online at http://www.mayomedicallaboratories.com/interpretive-guide/?alpha=H&unit_code=9180. Accessed January 2017.
Lichtin, A.E. (2013 October). Sickle cell disease. Merck Manual Professional Version. Available online at http://www.merckmanuals.com/professional/hematology-and-oncology/anemias-caused-by-hemolysis/sickle-cell-disease. Accessed January 2017.
Gersten, T. (Updated 2016 February 1). Sickle cell anemia. MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000527.htm. Accessed January 2017.
Gersten, T. (Updated 2016 February 11). Sickle cell test. MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003666.htm. Accessed January 2017.
(Updated 2016 August 31). Sickle cell disease. Centers for Disease Control and Prevention. Available online at http://www.cdc.gov/ncbddd/sicklecell/treatments.html. Accessed January 2017.
Maakaron, J.E. (Updated 2016 October 3). Sickle cell anemia workup. Medscape. Available online at http://emedicine.medscape.com/article/205926-workup. Accessed January 2017.
Mayo Clinic Staff. (2016 December 29). Sickle cell anemia. Diagnosis. Available online at http://www.mayoclinic.org/diseases-conditions/sickle-cell-anemia/diagnosis-treatment/diagnosis/dxc-20303501. Accessed January 2017.
(Updated January 2017). Hemoglobinopathies. Arup Consult. Available online at https://arupconsult.com/content/hemoglobinopathies?tab=tab_item-2. Accessed January 2017.
Sources Used in Previous Reviews
(2006 May). What is Sickle Cell Anemia. National Heart, Lung and Blood Institute Information Center [On-line information]. Available online at http://www.nhlbi.nih.gov/health/dci/Diseases/Sca/SCA_WhatIs.html.
Bender, M.A. (2006 March 7, Updated). Sickle Cell Disease. GeneReviews [On-line information]. Available online through http://www.genetests.org.
(© 2006). Hemoglobin Evaluation. ARUP’s Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.aruplab.com/guides/clt/tests/clt_a307.jsp#1150784.
(2004). Interpretation of Newborn Hemoglobin Screening Results. Michigan Department of Community Health [On-line information]. Available online through http://www.michigan.gov.
(2004 August). Sickle Cell Disease. March of Dimes, Quick Reference Fact Sheets [On-line information]. Available online at http://www.marchofdimes.com/professionals/681_1221.asp.
Raj, A. and Bertolone, S. (Updated 2009 July 9). Sickle Cell Anemia. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/958614-overview. Accessed September 2009.
Bender, M. A. and Hobbs, W. (Updated 2009 August 6). Sickle Cell Disease GeneReviews [On-line information]. Available online at http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene∂=sickle. Accessed September 2009.
Hildreth, C. et. al. (2008 December 10). Sickle Cell Vasculopathy. JAMA. 2008;300(22):2690 [On-line information]. PDF available for download at http://jama.ama-assn.org/cgi/reprint/300/22/2690.pdf. Accessed September 2009.
Mayo Clinic Staff (2009 April 1). Sickle cell anemia. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/sickle-cell-anemia/DS00324/METHOD=print. Accessed September 2009.
(2008 February). Sickle Cell Disease. March of Dimes Fact Sheets [On-line information]. Available online at http://www.marchofdimes.com/professionals/14332_1221.asp. Accessed September 2009.
(Reviewed 2009 June 9). Sickle Cell Disease: 10 Things You Need to Know. CDC [On-line information]. Available online at http://www.cdc.gov/Features/Sicklecell/. Accessed September 2009.
(2008 August). Sickle Cell Anemia. National Heart, Lung, and Blood Institute [On-line information]. Available online at http://www.nhlbi.nih.gov/health/dci/Diseases/Sca/SCA_WhatIs.html. Accessed September 2009.
Pagana, K. D. & Pagana, T. J. (© 2007). Mosby’s Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 523-525.
Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 219-223.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 518-521.
(October 5, 2009) National Guideline Clearinghouse. Screening for sickle cell disease in newborns: U.S. Preventive Services Task Force recommendation statement. Available online at http://www.guideline.gov/summary/summary.aspx?doc_id=11371&nbr=005908&string=sickle+AND+cell+AND+anemia. Accessed October 2009.
Sickle Cell Anemia. (Updated Feb. 7, 2012). MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000527.htm. Accessed August 2013.
Sickle Cell Disease. (Updated Sept. 15, 2011). Centers for Disease Control and Prevention. Available online at http://www.cdc.gov/ncbddd/sicklecell/treatments.html. Accessed August 2013.
Sickle Cell Test. (Updated Feb. 28, 2011). MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003666.htm. Accessed August 2013.
Sickle cell anemia on rise in newborns worldwide. (Published July 16, 2013). U.S. News and World Report Online. Available at http://health.usnews.com/health-news/news/articles/2013/07/16/sickle-cell-anemia-on-rise-in-newborns-worldwide. Accessed August 2013.
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