Which pattern is most consistent with thalassemia?

Which pattern is most consistent with thalassemia?

• A. Low Hematocrit, Low MCV, RDW High
• B. Low Hematocrit, Normal MCV, RDW Low
• C. Low Hematocrit, Low MCV, RDW Normal
• D. Low Hematocrit, Low MCV, RDW Normal or Low

Answer: (C)

Thalassemia trait typically causes a microcytic, hypochromic anemia with a normal RDW. The key idea is that the red cells are uniformly smaller due to the defect in globin synthesis, so you see a low hematocrit and a low MCV, but the variation in cell size is not large, keeping RDW normal. That combination—low hematocrit, low MCV, and a normal RDW—matches the pattern most consistently. If RDW were high, it would suggest mixed causes like iron deficiency with anisocytosis, which is less characteristic of isolated thalassemia. Thus, the pattern with low hematocrit, low MCV, and normal RDW is the best fit.

Thalassemia trait typically causes a microcytic, hypochromic anemia with a normal RDW. The key idea is that the red cells are uniformly smaller due to the defect in globin synthesis, so you see a low hematocrit and a low MCV, but the variation in cell size is not large, keeping RDW normal. That combination—low hematocrit, low MCV, and a normal RDW—matches the pattern most consistently. If RDW were high, it would suggest mixed causes like iron deficiency with anisocytosis, which is less characteristic of isolated thalassemia. Thus, the pattern with low hematocrit, low MCV, and normal RDW is the best fit.