Does being a sickle cell trait carrier impact blood work, such as Complete Blood Count (CBC) or hemoglobin electrophoresis?

Impact of Sickle Cell Trait on Blood Work

Sickle cell trait (SCT) carriers typically have normal complete blood counts (CBC) with minimal to no impact on routine blood work, though hemoglobin electrophoresis will show 30-40% hemoglobin S (HbS) along with normal adult hemoglobin (HbA). 1

Characteristics of Sickle Cell Trait

• Sickle cell trait (HbAS) is the heterozygous carrier state for the sickle cell gene, affecting approximately 1 in 13 African Americans in the United States 2
• Carriers have one normal beta-globin gene and one abnormal beta-globin gene (βs) that produces hemoglobin S 1
• The typical hemoglobin composition in SCT carriers shows:
  • 55-65% normal adult hemoglobin (HbA)
  • 30-40% sickle hemoglobin (HbS)
  • <1% fetal hemoglobin (HbF)
  • <3-5% other hemoglobins 1

Impact on Laboratory Tests

Complete Blood Count (CBC)

• SCT carriers typically have normal hemoglobin levels and red blood cell indices 1
• Unlike sickle cell disease, SCT does not cause anemia or significant changes to red blood cell morphology under normal conditions 1
• No significant impact on white blood cell or platelet counts 1

Hemoglobin Electrophoresis

• Hemoglobin electrophoresis will definitively identify the presence of HbS in carriers 1
• The percentage of HbS in carriers typically ranges from 30-40% of total hemoglobin 1, 3
• This test is essential for distinguishing between sickle cell trait and sickle cell disease, where HbS percentages are much higher (80-95% in HbSS) 1

A1C Testing Considerations

• African Americans with SCT may have A1C values approximately 0.3% lower than expected for a given level of glycemia 1
• This can potentially affect diabetes diagnosis and monitoring in individuals with SCT 1
• When marked discrepancies exist between measured A1C and plasma glucose levels in SCT carriers, alternative assays without interference or direct plasma glucose measurements should be used 1

Special Considerations

• Solubility testing for HbS (used in blood donation screening) can sometimes produce false positive results in individuals with other hemoglobin variants 4
• Some rare hemoglobin variants combined with HbS can produce more severe clinical manifestations even in heterozygotes 5
• Military service regulations previously limited individuals with >41% HbS, which would exclude approximately 20-40% of individuals with sickle cell trait 3

Clinical Significance

• SCT is generally considered a benign condition under normal physiological conditions 1
• Universal newborn screening programs identify both sickle cell disease and sickle cell trait 2
• The period following newborn screening provides an opportunity for education about potential health implications and reproductive considerations for families of identified SCT carriers 2

Common Pitfalls

• Confusing sickle cell trait with sickle cell disease in laboratory interpretation 1
• Failing to recognize that certain hemoglobin assays may be affected by the presence of HbS 1
• Not considering SCT when there are unexplained discrepancies between A1C and plasma glucose measurements in patients of African descent 1
• Overlooking the need for specialized hemoglobin assays without interference from hemoglobin variants when monitoring diabetes in SCT carriers 1