Does being a sickle cell trait carrier impact blood work?

Impact of Sickle Cell Trait on Blood Work

Being a sickle cell trait carrier can impact blood work results, particularly affecting A1C measurements and potentially causing discrepancies between A1C and actual blood glucose levels.

Effects on A1C Testing

• African Americans with sickle cell trait (HbAS) may have lower A1C values by approximately 0.3% compared to those without the trait for any given level of mean glycemia 1
• This discrepancy occurs because the presence of hemoglobin S variant can interfere with some A1C assay methods 1
• For patients with sickle cell trait who have normal red blood cell turnover, an A1C assay without interference from hemoglobin variants should be used 1

Other Blood Work Considerations

• Individuals with sickle cell trait typically have 20-40% hemoglobin S (HbS), with the remainder being normal adult hemoglobin (HbA) 2
• Complete blood count (CBC) results are generally normal in sickle cell trait carriers, as the condition is usually benign 3, 4
• Blood viscosity may be higher in untrained sickle cell trait carriers compared to non-carriers, which could potentially affect some hematological parameters 5

Clinical Implications

• When monitoring for diabetes in patients with sickle cell trait:

  • Marked discrepancies between measured A1C and plasma glucose levels should prompt consideration that the A1C assay may not be reliable 1
  • Alternative methods such as fasting plasma glucose, 2-hour plasma glucose tests, or fructosamine may be more accurate 1
  • An updated list of A1C assays with interferences is available at www.ngsp.org/interf.asp 1

• Other genetic variants can also affect A1C results:

  • X-linked glucose-6-phosphate dehydrogenase G202A, carried by 11% of African Americans, can decrease A1C by about 0.8% in homozygous men and 0.7% in homozygous women 1

Important Distinctions

• Sickle cell trait (heterozygous HbAS) is generally benign and should not be confused with sickle cell disease (homozygous HbSS or compound heterozygous states) 3
• A1C cannot be measured at all in individuals with sickle cell disease (HbSS) or other homozygous hemoglobin variants, as these individuals lack HbA 1

Recommendations for Healthcare Providers

• For patients with known sickle cell trait requiring diabetes monitoring:

  • Use A1C assays that are not affected by hemoglobin variants 1
  • Consider using plasma glucose criteria or alternative glycemic markers when there is concern about A1C accuracy 1
  • Be aware that A1C values may underestimate actual glycemic control in these patients 1

• When unexpected A1C results are encountered:

  • Consider hemoglobinopathy screening, especially in patients of African, Mediterranean, Middle Eastern, or Indian descent 3
  • Verify results with direct glucose measurements when discrepancies arise 1