How is microcytic anemia defined based on the MCV?
MCV < 80 fL
What should be the initial test for microcytic anemia?
Iron studies
If resources are limited, consider obtaining serum ferritin alone as the initial test. Although iron deficiency anemia is confirmed by low ferritin, elevated ferritin does not rule it out.
How is iron deficiency anemia diagnosed?
↓ Ferritin OR normal/↑ ferritin and ↑ TIBC
How is anemia of chronic disease diagnosed?
Normal/↑ ferritin and ↓ TIBC
What do both iron deficiency anemia and anemia of chronic disease have in common?
Serum iron levels are decreased in iron deficiency anemia and anemia of chronic disease.
Peripheral blood smears (PBS), reticulocyte count and red blood cell distribution width(RDW) are NOT routinely required to evaluate microcytic anemia because findings are often nonspecific. However, these tests are frequently obtained as part of the workup for anemia. What do PBS findings suggest?
PBS findings may suggest a specific etiology
E.g., basophilic stippling is seen in lead poisoning, sideroblastic anemia, thalassemias, and myelodysplastic syndromes.
What does a low reticulocyte count (< 2%) indicate concerning microcytic anemia?
iron deficiency anemia, thalassemia trait, anemia of chronic disease, sideroblastic anemia, and lead poisoning
What does a high reticulocyte count (< 2%) indicate concerning microcytic anemia?
thalassemia
What does the RDW concerning microcytic anemia indicate?
typically high in iron deficiency anemia and sideroblastic anemia
When should a hemoglobin electrophoresis be obtained?
obtain if serum iron levels, TIBC, and TfS are normal or elevated
What does a normal hemoglobin A2 indicate?
Sideroblastic anemia, α-thalassemia trait
What does an increased hemoglobin A2 indicate?
β-thalassemia trait
When should a bone marrow biopsy be considered?
If the following are identified:
Ringed sideroblasts on PBS (see sideroblastic anemia, myelodysplastic syndromes)
Unexplained thrombocytopenia, leukocytopenia, or pancytopenia
Numerous immature forms of blood cells on CBC and/or PBS
When should serum lead levels be considered?
consider in patients with basophilic stippling but no ringed sideroblasts on PBS
What are the most common causes of microcytic anemia?
Iron deficiency anemia + thalassemia trait
How is it possible to distinguish between lead poisoning or sideroblastic anemia?
Basophilic stippling on peripheral blood smear suggests lead poisoning or sideroblastic anemia. Because ringed sideroblasts are not usually seen in lead poisoning, they can help to distinguish between this condition and sideroblastic anemia.
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