Peripheral Blood Smear Review
Systematic approach to blood film interpretation
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PathologyDiagnostic
Peripheral Blood Smear Interpretation Algorithm
Peripheral Blood Smear Interpretation Algorithm: Peripheral Blood Smear Review → Smear Quality Assessment → RBC Assessment → RBC Morphology Patterns → C...
Pathway Overview
10 steps
Algorithm Steps
10 total
01Start 02Decision Smear Quality Assessment
Evaluate technical adequacy
- Good feathered edge
- Monolayer zone present
- No clotting or artifacts
- Staining quality adequate
03Action RBC Assessment
Evaluate red cell morphology
- Size: Microcytic, normocytic, macrocytic
- Shape: Spherocytes, elliptocytes, sickle cells, schistocytes
- Color: Hypochromic, polychromatic
- Inclusions: Howell-Jolly, basophilic stippling, parasites
- Distribution: Rouleaux, agglutination
04Decision RBC Morphology Patterns
Recognize diagnostic patterns
- Spherocytes → Hereditary spherocytosis, AIHA
- Schistocytes → MAHA (TTP, HUS, DIC)
- Target cells → Liver disease, hemoglobinopathy
- Sickle cells → Sickle cell disease
- Teardrop cells → Myelofibrosis
05Warning Critical/Urgent Findings
Require immediate notification
- Blasts present (possible leukemia)
- >1% schistocytes (MAHA)
- Malaria parasites
- Extreme leukocytosis (>100K)
- Marked thrombocytopenia with bleeding risk
06Action Correlate with CBC/Clinical
Integrate findings
- Match morphology with indices (MCV, MCH, MCHC)
- Review clinical history
- Consider additional testing: reticulocyte count, hemolysis labs
- Recommend flow cytometry if abnormal WBCs
- Suggest bone marrow if indicated
07Outcome Issue Report
Document findings and recommendations
- Path rejoins step 06Shared downstream outcome
08Action WBC Assessment
Evaluate white cell morphology
- Differential count estimation
- Immature forms: Left shift, blasts
- Toxic changes: Döhle bodies, toxic granulation, vacuoles
- Atypical lymphocytes
- Abnormal cells: Leukemia, lymphoma
09Decision WBC Pattern Recognition
Identify significant findings
- Blasts >5% → Leukemia workup
- Left shift → Infection, CML
- Atypical lymphs → Viral (EBV, CMV), lymphoma
- Monocytosis → CMML, chronic infection
- Eosinophilia → Allergy, parasites, neoplasm
- Path rejoins step 05Shared downstream outcome
- Path rejoins step 06Shared downstream outcome
10Action Platelet Assessment
Evaluate platelet morphology
- Quantity: Adequate, increased, decreased
- Size: Large platelets, giant platelets
- Clumping: Pseudothrombocytopenia
- Granulation: Hypogranular (MDS)
- Exclude platelet satellitism
- Path rejoins step 06Shared downstream outcome
Guideline Source
ASCP Peripheral Blood Smear Review Guidelines
Clinical Safety Information
Clinical Decision Support — Not a Substitute for Clinical Judgment
Individual patient factors may require deviation from these recommendations.
Known Limitations
- Requires adequate smear quality for interpretation
- Does not replace flow cytometry for leukemia diagnosis
- Quantitative abnormalities need CBC correlation
- Rare morphologies may require specialist review
- Does not address bone marrow correlation
Applicable Regions
USAUUKEU
AU: RCPA guidelines
UK: NICE hematology pathways
US: ASCP and CAP guidelines
Version 1Next review: 2028-01-01
Next steps
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Related Resources
Frequently Asked Questions
What is the Peripheral Blood Smear Interpretation Algorithm?
The Peripheral Blood Smear Interpretation Algorithm is a diagnostic clinical algorithm for Pathology. It provides a structured decision tree to guide clinical decision-making, based on ASCP Peripheral Blood Smear Review Guidelines.
What guideline is the Peripheral Blood Smear Interpretation Algorithm based on?
This algorithm is based on ASCP Peripheral Blood Smear Review Guidelines (DOI: 10.1093/ajcp/aqz203).
What are the limitations of the Peripheral Blood Smear Interpretation Algorithm?
Known limitations include: Requires adequate smear quality for interpretation; Does not replace flow cytometry for leukemia diagnosis; Quantitative abnormalities need CBC correlation; Rare morphologies may require specialist review; Does not address bone marrow correlation. Individual patient factors may require deviation from these recommendations.
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