From the Guidelines
A peripheral blood smear is typically ordered to evaluate abnormalities detected on a complete blood count (CBC) or when certain clinical conditions are suspected, as strongly recommended by the most recent guidelines 1. The main reasons for ordering a peripheral smear include investigating unexplained cytopenias (low blood cell counts) or cytoses (elevated counts), evaluating abnormal cell morphology, diagnosing specific hematologic disorders like leukemias or hemolytic anemias, and monitoring response to treatment. Some key points to consider when deciding to order a peripheral smear include:
- Investigating unexplained symptoms like fatigue or bleeding
- Evaluating red cell abnormalities such as spherocytes, schistocytes, or sickle cells
- Assessing white cell disorders including leukemias and infections
- Examining platelet abnormalities in size, number, or morphology
- Confirming potential abnormalities flagged by automated analyzers
- Monitoring known hematologic conditions The smear provides direct visualization of blood cells under microscopy, offering information about cell size, shape, inclusions, and maturity that automated counts cannot provide, making it an essential diagnostic tool in hematology, as highlighted in various guidelines 1. In clinical practice, the decision to order a peripheral smear should be based on the most recent and highest quality evidence available, with consideration of the patient's specific clinical context and potential risks and benefits, as emphasized in the guidelines 1.
From the Research
Main Reasons to Order a Peripheral Smear
The main reasons to order a peripheral smear include:
- Evaluation of bleeding disorders, anemia, infectious disorders, and suspected leukemia 2
- Investigation of clinical scenarios such as isolated thrombocytopenia, unexplained bruises, acute febrile illnesses, and anemia 3
- Verification of flagged automated hematology results and determination of the need for a manual differential leukocyte count 4
- Diagnosis or diagnostic clue of haematological cancers, including lymphoma, leukemia, myeloma, myelodysplastic syndromes, and myeloproliferative neoplasms 5
- Evaluation of hematologic and non-hematologic disorders, with potential added clinical value in cases with morphologic abnormalities that cannot be diagnosed by automated laboratory testing alone 6
Specific Indications for Peripheral Smear
Specific indications for peripheral smear include:
- White blood cell abnormalities, with 25% of smear reviews having potential added clinical value 6
- Red blood cell abnormalities, with 19% of smear reviews having potential added clinical value 6
- Platelet abnormalities, with 13% of smear reviews having potential added clinical value 6
- Suspected leukemia, with peripheral blood smear review being an important diagnostic tool 2, 3