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Simon Senanu: Diagnostic Significance of Target Cells in Peripheral Blood Smear
Simon Senanu
Mar 22, 2026, 15:48

Simon Senanu: Diagnostic Significance of Target Cells in Peripheral Blood Smear

Simon Senanu, Medical Laboratory Scientist at Perkins Medical Centre, shared a post on LinkedIn:

“Target cells (codocytes) – what that ‘bullseye’ really means

On a peripheral blood smear, some red blood cells display a distinctive central area of hemoglobin surrounded by a clear zone and a peripheral ring – giving a ‘bullseye’ appearance.

These are known as target cells (codocytes).

While visually striking, they are more than just morphology – they provide important diagnostic clues.

What Are Target Cells?

Target cells are red blood cells with excess membrane relative to cell volume.

This altered surface area-to-volume ratio causes hemoglobin to redistribute, forming the characteristic central staining pattern.

Mechanism of formation

Target cells form due to:

  • Increased red cell membrane

or

  • Reduced intracellular hemoglobin

This imbalance leads to folding of the membrane, producing the ‘target’ appearance.

Conditions associated with target cells

Target cells are seen in several clinical conditions, including:

  • Liver disease – excess cholesterol incorporation into RBC membrane
  • Thalassemia – reduced globin chain synthesis
  • Hemoglobinopathies (e.g., HbS, HbC)
  • Iron deficiency anemia (less prominent than in thalassemia)
  • Post-splenectomy states

Peripheral smear clues

The pattern and abundance of target cells can guide diagnosis:

  • Numerous target cells – think thalassemia or hemoglobinopathy
  • Moderate numbers – consider liver disease
  • Occasional cells – may be seen in iron deficiency

Always interpret alongside:

  • RBC indices
  • Clinical history
  • Other smear findings

Laboratory pitfall

Target cells can sometimes be artifactual, especially in poorly prepared smears.

Key clue:

  • True target cells are consistent across the smear
  • Artifacts are irregular and unevenly distributed

Clinical significance

Target cells are not a diagnosis, they are a morphological signal.

Their presence should prompt evaluation for:

  • Hemoglobin disorders
  • Liver dysfunction
  • Disorders of red cell production

Laboratory takeaway

When you see target cells, think in terms of membrane vs hemoglobin imbalance.

Morphology, when combined with laboratory data, becomes a powerful diagnostic tool.

When you see numerous target cells on a smear, do you first think thalassemia or liver disease?”

Simon Senanu: Diagnostic Significance of Target Cells in Peripheral Blood Smear

Other posts featuring Simon Senanu on Hemostasis Today.

codocytes Health Hematology Hemoglobin disorders Hemoglobinopathies Hemostasis News Hemostasis Today IDA Iron-Deficiency Anemia Liver Disease Medicine Nucleated RBCs PBS Peripheral Blood Smear RBC Simon Senanu Target cells Thalassemia
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