Impact of Sickle Cell Trait on Blood Work

Effects on A1C Testing

African Americans with sickle cell trait may have lower A1C values by approximately 0.3% compared to those without the trait for any given level of mean glycemia 1
The presence of hemoglobin S variant can interfere with some A1C assay methods, affecting the accuracy of A1C measurements 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

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 for patients with sickle cell trait 1, 3
Other genetic variants, such as X-linked glucose-6-phosphate dehydrogenase G202A, can also affect A1C results, decreasing A1C by about 0.8% in homozygous men and 0.7% in homozygous women 1

A1C cannot be measured at all in individuals with sickle cell disease, as these individuals lack HbA 3

For patients with known sickle cell trait requiring diabetes monitoring, A1C assays that are not affected by hemoglobin variants should be used 1
Healthcare providers should consider using plasma glucose criteria or alternative glycemic markers when there is concern about A1C accuracy in patients with sickle cell trait 1
A1C values may underestimate actual glycemic control in patients with sickle cell trait 1