peripheral smear
Summary
A peripheral blood smear is a microscopic examination of a thin blood film stained (usually with Wright-Giemsa stain) to evaluate the morphology, number, and size of red blood cells, white blood cells, and platelets. It is a key diagnostic tool for anemia, infections, leukemias, and other hematologic disorders.
Detail
A peripheral smear involves spreading a drop of blood thinly on a glass slide, staining it, and examining it under a microscope. It allows assessment of RBC morphology (size, shape, color, inclusions), WBC differential and morphology, and platelet number/morphology. Key findings include: schistocytes (microangiopathic hemolytic anemia, DIC, TTP/HUS), spherocytes (hereditary spherocytosis, autoimmune hemolytic anemia), target cells (thalassemia, liver disease, HbC disease), sickle cells (sickle cell disease), teardrop cells (myelofibrosis), Howell-Jolly bodies (asplenia), basophilic stippling (lead poisoning, thalassemia), Heinz bodies (G6PD deficiency), and Auer rods (acute myeloid leukemia). Smears also help identify blast cells (leukemia), hypersegmented neutrophils (megaloblastic anemia), and parasites (malaria, babesiosis). It complements CBC data by providing direct visual confirmation of abnormalities, especially important when automated counters flag abnormal results. Clinically, it is essential in the workup of anemia, thrombocytopenia, leukocytosis, and suspected hemolysis or infection, guiding further testing and diagnosis.
Sources
- First Aid for the USMLE Step 1
- Robbins Basic Pathology
- Harrison's Principles of Internal Medicine
- UpToDate: Approach to the peripheral blood smear
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