Indicates that the cells express the mutated gene for sickle hemoglobin (HbS), either in homozygous form (HbSS) or as a compound with another abnormal beta hemoglobin form. The number of these abnormal cells should not necessarily be considered an indicator of severity, but increased numbers of abnormal cells and polychromasia (or nucleated red cells) often occur during sickle crises.

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Conditions with sickle hemoglobin

Sickle cell disease (HbSS)

• The typical disorder (features as described above). Sickle cell/hemoglobin C disease (SC disease): may be difficult to distinguish from typical sickle cell disease. Look for more prominent target cells and/or boat-shaped cells as well as branched SC poikilocytes. Typical sickle cells, nucleated red cells, polychromasia, and features of splenectomy are less prominent.

Sickle/beta thalassemia 

• Morphological distinction from uncomplicated sickle cell disease may not be possible, but suspect this if there is significant microcytosis and hypochromia, and target cells. Sickle cells may be less frequent.

Heterozygous (sickle cell trait)

• There may be sickle cells if subjected to profound hypoxia, but this is very uncommon. Cells with boat-like shape may be found, but many individuals have normal blood slide appearances.