A CBC shows HbS 39%, HbA 60%, HbF 1% with a positive Sickledex result. What is the most likely diagnosis?

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Multiple Choice

A CBC shows HbS 39%, HbA 60%, HbF 1% with a positive Sickledex result. What is the most likely diagnosis?

The key idea is using the pattern of hemoglobins on electrophoresis to distinguish sickle cell trait from disease. Sickledex detects the presence of HbS, but it doesn’t tell you whether you’re homozygous for HbS (disease) or heterozygous (trait). In trait, HbA remains the majority while HbS is present in a significant but smaller amount; in disease, HbS is overwhelmingly dominant and HbA is essentially absent. Here, HbS is about 39% and HbA is 60%, with a normal-level HbF of 1%. This ratio fits sickle cell trait (HbAS) well: there is HbS present but HbA remains the principal hemoglobin. The absence of HbC and the low HbF further support trait rather than HbSC or beta-thalassemia trait. Therefore, the most likely diagnosis is sickle cell trait.

The key idea is using the pattern of hemoglobins on electrophoresis to distinguish sickle cell trait from disease. Sickledex detects the presence of HbS, but it doesn’t tell you whether you’re homozygous for HbS (disease) or heterozygous (trait). In trait, HbA remains the majority while HbS is present in a significant but smaller amount; in disease, HbS is overwhelmingly dominant and HbA is essentially absent.

Here, HbS is about 39% and HbA is 60%, with a normal-level HbF of 1%. This ratio fits sickle cell trait (HbAS) well: there is HbS present but HbA remains the principal hemoglobin. The absence of HbC and the low HbF further support trait rather than HbSC or beta-thalassemia trait. Therefore, the most likely diagnosis is sickle cell trait.

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