Sickle cell disease (SCD) is a group of inherited red blood cell disorders affecting hemoglobin, the protein responsible for carrying oxygen. SCD causes normally round, flexible red blood cells to become stiff, sticky, and crescent-shaped. These sickled cells can block blood flow, leading to pain episodes and organ damage. Sickle cell trait (SCT) means a person is a carrier, having received one sickle cell gene and one normal gene, but does not have the disease. Testing is necessary to diagnose SCD, identify carriers, and help families make informed health and reproductive decisions.
Who Should Be Tested and When
Testing for SCD and SCT is performed at various life stages to ensure early detection. Newborn screening is mandatory in all U.S. states and territories, where a blood sample is collected shortly after birth. This early testing is important because timely intervention, such as preventive penicillin, can significantly reduce mortality in infants with SCD.
Testing is also recommended for prospective parents, especially those with a family history of the disorder. Individuals of African, Mediterranean, Middle Eastern, or South Asian descent have a higher prevalence of the sickle cell gene and should consider carrier screening. Prenatal screening is available for expectant parents who are known carriers, often involving sampling amniotic fluid or placental tissue to determine the baby’s status before birth. Adults who do not know their status can request a simple blood test from their healthcare provider at any time.
Understanding the Testing Process
Testing involves collecting a blood sample to analyze the hemoglobin. For newborns, this is typically done through a heel prick to obtain blood on a special card, known as a dried blood spot. For older children and adults, the sample is usually taken from a vein in the arm. The collected sample is then sent to a specialized laboratory for detailed analysis.
The laboratory uses advanced methods to identify and quantify the different types of hemoglobin present. Techniques like hemoglobin electrophoresis, high-performance liquid chromatography (HPLC), and isoelectric focusing are commonly used to separate hemoglobin types based on their electrical charge. These methods accurately differentiate between normal hemoglobin (HbA), sickle hemoglobin (HbS), and other variants. If initial screening tests are positive, a confirmatory test like HPLC is performed to provide a definitive diagnosis of SCD or SCT.
Accessing Testing and Interpreting Results
Individuals can obtain a sickle cell test through their primary care physician, specialized hematology clinics, public health screening programs, or community health centers. Pregnant women are typically offered screening as part of their routine prenatal care. Initial screening results are generally available within a few days to a week.
Interpreting the results depends on the types of hemoglobin identified in the sample. A negative result means the person does not have the sickle cell gene. A diagnosis of Sickle Cell Trait (SCT) indicates the presence of both normal hemoglobin (HbA) and sickle hemoglobin (HbS), meaning the person is a carrier. Sickle Cell Disease (SCD) is diagnosed when two abnormal hemoglobin genes are detected, often resulting in mostly HbS in the blood.
A positive result for either SCT or SCD warrants a referral for genetic counseling. A genetic counselor explains the implications of the results, details the risk of passing the gene to future children, and discusses reproductive options. For those diagnosed with SCD, the healthcare provider will recommend immediate follow-up care, including specialized treatments and long-term disease management.