Peripheral Blood Smear: Red Blood Cell Morphology – Interpretation & Clinical Use
Synonyms
Blood Smear Morphology, Peripheral Smear, RBC Smear, RBC Morphology, Red Blood Cell Morphology
Applies to
- Ovalocytes Smear
- Schistocytes Smear
- Sickle Cells Smear
- Spherocytes Smear
- Stippled RBCs Smear
Specimen
Whole blood
Container
Lavender top (EDTA) tube; prepared via fingerstick, heelstick, or venipuncture.
Note: Oxalate or heparin may deform WBCs artificially.
Collection
Venipuncture; gently invert tube to mix anticoagulant with blood.
Storage Instructions
Refrigerate until processed.
Reason to Reject Sample
- Clotted specimen
- Hemolyzed sample
Reference Range
Normal red blood cell morphology. Minor changes, such as 5–10% elliptocytosis, may not indicate disease.
Use
- Evaluate red blood cell disorders
- Support CBC parameters (MCV, MCH, MCHC, RDW)
- Examine platelet and WBC disorders
- Confirm CBC findings as a quality control measure
Methodology
Visual examination of red cells on Wright’s-stained peripheral smear.
Automated counters provide red cell indices (MCV, MCH, RDW) that correlate with morphology.
Additional Information
Manual peripheral blood smear (PBS) reviews play a crucial role in diagnosing hematologic disorders, especially where automated analyzers fall short. Though labor-intensive, PBS review offers a cost-effective and diagnostically rich method.
- Automated analyzers are capital-intensive but do not replace expert visual review.
- Parameters like RDW can enhance findings but do not replace direct morphological analysis.
- Manual smear review helps identify abnormalities missed by machines, such as:
- Anisocytosis
- Poikilocytosis
- Target cells, schistocytes, sickle cells
- Capillary blood smears may be less accurate due to platelet clumping and distribution artifacts.
- Manual PBS analysis remains a key quality assurance step in the CBC workflow.
Automated Systems vs Manual Review
- Automated differential counters may flag 10–20% of smears for manual review.
- Manual review is essential when abnormalities are detected or suspected.
- Quantitative Buffy Coat Analysis (QBCA) is an alternative low-cost method using fluorescence and specialized tubes.
Clinical and Economic Considerations
- Routine differential WBC count is not always cost-effective in outpatient settings.
- In hospitalized patients, however, PBS abnormalities are more prevalent and clinically valuable.
- The shift in healthcare reimbursement models emphasizes cost-benefit optimization of tests.
Integration with CBC
A complete hematological evaluation includes:
- Complete Blood Count (CBC)
- Red Cell Indices (MCV, MCH, MCHC, RDW)
- Peripheral Blood Smear (PBS)
- Differential Leukocyte Count
References
- Jacobs, Demott, Finley, Horvat, Kasten.JR, & Tilzer. “Laboratory Test Handbook.” Lexi-Comp Inc. 1994.
- Van Assendelft OW. “Interpretation of the Quantitative Blood Cell Count.” Practical Laboratory Hematology. Koepke JA, ed. Churchill Livingstone, 1991:78–98.
