Sickle Cell Test
1. Objective
The objective of the Sickle Cell Test was to detect the presence of Hemoglobin S (HbS), which caused sickle cell disease or sickle cell trait. The test aimed to screen or diagnose individuals who inherited the mutated beta-globin gene.
2. Principle
The principle of the test was based on the fact that Hemoglobin S polymerized under low oxygen tension, causing red blood cells to become crescent or sickle-shaped. These abnormally shaped cells were detected microscopically (sickling test), through solubility tests, or by electrophoresis to differentiate hemoglobin types.
3. Materials
• Anticoagulated blood sample (EDTA)
• Sodium metabisulfite (for sickling test)
• Microscope and glass slides
• Hemoglobin electrophoresis equipment (for confirmatory test)
• Solubility test reagent kit (for rapid screening)
• Coverslips
• Test tubes and pipettes
• Gloves and safety equipment
4. Procedure (Microscopic Sickling Test)
1. A drop of the patient’s blood was placed on a clean glass slide.
2. A drop of 2% sodium metabisulfite solution was added to deoxygenate the blood.
3. The mixture was covered with a coverslip and sealed to prevent oxygen entry.
4. The slide was incubated at room temperature for 30 minutes to 1 hour.
5. The slide was examined under a microscope for the presence of sickle-shaped red blood cells.
Alternative methods:
• In the solubility test, HbS became insoluble in a phosphate buffer and formed a turbid solution.
• In electrophoresis, different hemoglobins were separated based on their migration pattern under an electric field.
5. Result
• Positive Test (Sickle Cell Disease): Numerous sickle-shaped RBCs were seen; solubility test showed turbidity; electrophoresis confirmed HbSS.
• Positive for Trait (Carrier): Few sickled cells were seen; electrophoresis showed both HbA and HbS (HbAS).
• Negative Test: Normal round RBCs; clear solubility test; electrophoresis showed HbA only.
6. Uses
• Diagnosed sickle cell disease (HbSS) and sickle cell trait (HbAS)
• Screened newborns and high-risk populations (e.g., Africans, Indians, Middle Easterners)
• Evaluated unexplained hemolytic anemia, pain crises, or joint swelling
• Assessed family members of affected individuals
• Guided genetic counseling and prenatal screening
7. Consultation
Positive results required consultation with a hematologist or genetic counselor. Further evaluation like complete blood count (CBC), reticulocyte count, and DNA analysis might have been recommended. Patient education and long-term management strategies were also discussed in case of sickle cell disease.
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