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PA13.1-3 | Hematopoiesis & Blood Specimen Basics — Part 3

Peripheral Blood Smear Preparation: Setting Up the Haematologist's View

The peripheral blood smear (PBS) or peripheral blood film (PBF) is the haematologist's primary diagnostic tool — it lets you examine every cell line morphologically. Collecting blood into the correct tube is step one; preparing a quality smear is step two.

Making a wedge smear (standard technique):

1. Place a drop (~5 µL, about a small drop) of fresh EDTA-anticoagulated blood 1 cm from the frosted end of a clean glass slide
2. Angle the spreader slide at 30–45° to the first slide, touching the drop
3. Allow the blood to spread along the width of the spreader by capillary action
4. Push the spreader in one smooth, continuous motion toward the far end of the slide — don't stop mid-way
5. Air-dry immediately — do NOT blow on the smear (breath moisture distorts RBCs)
6. Fix and stain with Leishman or Giemsa stain

Recognising a good smear:
• Should have a head (thick end), body (reading area), and tail (thin end, where cells become monolayer)
• The reading area is where cells are evenly distributed, not touching each other, with a visible central pallor in RBCs
• Cell count per field: 200–250 red cells, with WBCs easily distinguishable

Common smear artefacts and their causes:
• Too thick — too much blood OR spreader angle >45° → RBCs stack as rouleaux, WBCs obscured
• Holes in the smear — dirty or greasy slide → artefactual cell-free areas
• Crenated RBCs — delayed spreading, acidic stain, or slow drying → mistaken for acanthocytes
• Uneven staining — slide touched with bare hands (skin oils) → background deposits

Wedge Blood Smear Preparation Technique