Evaluation of the peripheral blood smear
Examination of the peripheral blood smear is a powerful diagnostic tool. it often provides rapid, reliable access to information about a
variety of hematologic disorders. The smear offers a window into the functional status of the bone marrow, the factory producing all
blood elements. It is particularly important when assessing cytopenic states (eg, anemia, leukopenia, thrombocytopenia).
Review of the smear is an important adjunct to other clinical data; in some cases, the peripheral smear alone is sufficient to establish a
diagnosis. Review of the peripheral smear is not required in all patients with a hematological disorder. Certain straightforward conditions such as
iron deficiency anemia can be easily diagnosed on the basis of clinical information and basic laboratory data (eg, mean corpuscular
volume [MCV], serum ferritin) alone. However, there are a number of settings in which interpretation of the peripheral smear is
especially important. Two examples include:
Hemolytic anemia – Review of red cell morphology may identify the cause of erythrocyte destruction (eg, the presence of bite cells
points to a Heinz body hemolytic anemia) and the ultimate diagnosis (eg, oxidant damage to the red cell secondary to drugs).
Thrombocytopenia – Review of platelet size and morphology can sometimes suggest whether thrombocytopenia is due to increased
platelet consumption (generally associated with larger platelets) or reduced platelet production (often associated with smaller platelets
or abnormal platelet morphology).