Diagnosis of sicklecell anemia

Diagnosis of Sickle Cell Anemia

Sickle cell anemia can be diagnosed using a combination of simple laboratory tests that detect the presence of sickle-shaped red blood cells and abnormal hemoglobin (HbS). The most commonly used methods include:

1.     Sickling Test:

o    A microscopic examination of a blood smear is performed after adding a reducing agent such as sodium dithionite.

o    In individuals with sickle cell anemia or sickle cell trait, the erythrocytes adopt a characteristic sickle shape, which can be easily observed under the microscope.

2.     Hemoglobin Electrophoresis:

o    Hemoglobin samples are subjected to electrophoresis in an alkaline medium (pH 8.6).

o    Sickle cell hemoglobin (HbS) moves more slowly towards the anode (positive electrode) compared to normal adult hemoglobin (HbA).

o    The slower mobility of HbS is due to less negative charge, caused by the absence of glutamate residues that normally carry negative charges.

o    In individuals with sickle cell trait (heterozygous), both HbA (fast-moving) and HbS (slow-moving) are detected.

o    Electrophoresis of hemoglobin obtained from lysed erythrocytes is a routine and reliable method for diagnosing both sickle cell anemia and the sickle cell trait.

Visual Aid:

• Figure: Electrophoresis at pH 8.6
• HbA: Normal adult hemoglobin
• HbS: Sickle cell hemoglobin

FIG. - Electrophoresis of hemoglobins at pH 8.6 (HbA–Normal adult

hemoglobin; HbS–Sickle cell hemoglobin). 

Summary:
These diagnostic methods allow clinicians to identify sickled erythrocytes and abnormal hemoglobin, providing a definitive diagnosis for patients with sickle cell anemia or carriers of the sickle cell trait.