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Peripheral blood smear

Hematology · also called Blood film, PBF, Peripheral film, Manual differential

What it measures

A stained thin film of blood examined under the microscope to assess the shape and appearance of red cells, white cells and platelets. It confirms analyzer flags and reveals parasites, blasts and abnormal cells.

Specimen and preparation

Specimen: Whole blood (EDTA) or fingerprick
Tube: Lavender top
Preparation: Make films within 2–3 h of collection to avoid EDTA artifacts.

Reference range

Group	Range
All	Normocytic normochromic RBCs; normal WBC morphology and differential; adequate platelets; no abnormal cells or parasites

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

Blasts: acute leukemia
Schistocytes: DIC, TTP/HUS, mechanical hemolysis
Target cells: thalassemia, liver disease
Spherocytes: hereditary spherocytosis, autoimmune hemolysis
Hypersegmented neutrophils: B12/folate deficiency
Malaria or other blood parasites

Method

Wedge smear stained with Wright, Giemsa or Leishman stain; light microscopy

Good to know

Always report platelet clumps and nucleated red cells, as both distort automated counts. Blasts or parasites are critical findings.

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