Question

A patient has target cells, nucleated RBCs, and microcytic hypochromic anemia on the peripheral smear, along with a positive family history. What is the investigation of choice?

• A. Coombs test
• B. Osmotic fragility
• C. Hb electrophoresis
• D. Sucrose lysis test

Hint:

Target cells, nucleated RBCs and a family history point to an inherited hemoglobin disorder; pick the test that reads the hemoglobin pattern directly.

Answer 1

The Correct Option is C

Target cells, nucleated red cells, microcytic hypochromic anemia, and a positive family history together point toward an inherited hemoglobin disorder such as thalassemia. Let's check what each test actually tells us.

1. Coombs test: Detects antibody-coated red cells in autoimmune hemolysis, which has nothing to do with an inherited condition running in the family.
2. Osmotic fragility: Shows that red cells resist bursting in dilute saline, which happens in thalassemia because of the target cells, but this only screens; it cannot pin down the exact hemoglobin defect.
3. Hb electrophoresis: Separates the different hemoglobin fractions and directly shows the abnormal pattern, such as raised HbA2 or HbF, that confirms thalassemia.
4. Sucrose lysis test: Screens for paroxysmal nocturnal hemoglobinuria, an acquired red cell disorder, not an inherited one, so it does not fit this case.

Since the picture strongly suggests an inherited hemoglobinopathy, the test that actually proves it by reading the hemoglobin types is Hb electrophoresis.

Let's summarize:

• Target cells and nucleated RBCs with a family history point to thalassemia, not an autoimmune or acquired red cell disease.
• Only Hb electrophoresis directly identifies the abnormal hemoglobin fractions to confirm it.

The investigation of choice is Hb electrophoresis.