The Sickle Cell Screening (Sickling Test) is a simple blood test used to screen for Hemoglobin S (HbS), an abnormal form of hemoglobin. Hemoglobin is the protein inside red blood cells that carries oxygen throughout the body. When a person has HbS, some red blood cells can become stiff and “sickle” (crescent-shaped) under certain conditions, which may lead to anemia and problems with blood flow.

In a traditional sickling/solubility-style screening test, the lab uses a chemical environment that encourages HbS-containing red blood cells to change in a way that can be detected. The test is typically reported as:

Negative (no sickling/HbS not detected): HbS was not found by this screening method. This usually means you do not have sickle cell trait or sickle cell disease. However, no screening test is perfect, and follow-up testing may still be recommended if suspicion is high.

Positive (sickling/HbS detected): HbS is present. This does not by itself confirm whether you have sickle cell trait (carrier status) or sickle cell disease. A positive screen should be confirmed with a more specific test such as hemoglobin electrophoresis, HPLC (high-performance liquid chromatography), or molecular/genetic testing.

Because this is a screening test, it is best viewed as an initial “yes/no” check for HbS. Your clinician will interpret the result along with your symptoms, complete blood count (CBC), family history, and any newborn screening records.

Healthcare providers order sickle cell screening when there is a reason to suspect a sickle cell disorder, when someone is at increased genetic risk, or when screening is required as part of preventive care. Common situations include:

Risk factors and family history

This test may be recommended if you have a family history of sickle cell disease or sickle cell trait, or if your background is associated with a higher likelihood of carrying HbS, including people of African descent (and also individuals with ancestry from the Mediterranean, Middle East, India, and parts of Central/South America and the Caribbean). It may also be used as part of genetic screening and reproductive planning (for example, before pregnancy or early in pregnancy), since two carriers can have a child with sickle cell disease.

Newborn and childhood screening follow-up

In many regions, newborn screening already checks for sickle cell disease. A sickling test may be used later to confirm a history, to evaluate someone who was not screened as a newborn, or to investigate unclear past results.

Symptoms that may prompt testing

A clinician may consider screening if you have symptoms or findings suggestive of a hemoglobin disorder, such as:

• Unexplained anemia or low hemoglobin/hematocrit on a CBC
• Episodes of severe pain (possible vaso-occlusive pain crises), especially in bones, chest, or abdomen
• Frequent infections or delayed growth in children
• Shortness of breath, fatigue, or jaundice (yellowing of skin/eyes)
• History of splenic problems (enlargement or dysfunction) or certain complications like acute chest symptoms

Pre-participation and occupational evaluation

Some people are screened for sickle cell trait in specific settings (for example, certain athletic programs or occupations). Knowing trait status can help guide safe training and prevention strategies, especially around dehydration, heat stress, and extreme exertion.

• Sickle cell disease (including HbSS)
• Sickle cell trait (HbAS carrier state)
• Hemoglobin SC disease (HbSC)
• Sickle beta-thalassemia (HbS/β-thalassemia)
• Hemolytic anemia related to sickling disorders

• Early detection of sickle cell disorders to reduce complications through timely care
• Clarifying the cause of anemia and guiding appropriate follow-up testing
• Family planning and genetic counseling (understanding carrier status and reproductive risk)
• Newborn/child health management by confirming screening history and ensuring appropriate preventive steps
• Risk reduction during intense exercise and heat exposure by identifying sickle cell trait when relevant
• Connecting patients to specialist care (hematology) and preventive strategies such as vaccines and infection prevention when indicated