From the Guidelines
The utility of HbA1c testing is limited in patients with severe anemia, and it should not be used for diabetes diagnosis or monitoring in these patients due to potential inaccuracies caused by altered red blood cell turnover.
Limitations of HbA1c in Severe Anemia
The HbA1c test measures the percentage of hemoglobin that has glucose attached, which depends on both blood glucose levels and red blood cell lifespan, making it unreliable when red blood cell dynamics are abnormal 1.
- Conditions that affect red blood cell turnover, such as hemolytic and other anemias, can result in discrepancies between the HbA1c result and the patient’s true mean glycemia.
- In iron deficiency anemia, HbA1c may be falsely elevated, while in hemolytic anemia, it may be falsely decreased due to shortened red blood cell lifespan.
Alternative Methods for Glucose Monitoring
Alternative methods for glucose monitoring should be used instead, such as:
- Fasting plasma glucose
- Random glucose measurements
- Continuous glucose monitoring For patients with hemoglobinopathies or severe anemia, fructosamine or glycated albumin tests are better options as they reflect glucose control over 2-3 weeks and are not affected by red blood cell lifespan 1.
Clinical Considerations
Clinicians should exercise judgment when using HbA1c as the sole basis for assessing glycemic control, particularly if the result is close to the threshold that might prompt a change in medication therapy 1.
- Other measures of average glycemia, such as fructosamine and 1,5-anhydroglucitol, are available, but their translation into average glucose levels and their prognostic significance are not as clear as for HbA1c.
- HbA1c does not provide a measure of glycemic variability or hypoglycemia, and for patients prone to glycemic variability, glycemic control is best evaluated by the combination of results from self-monitoring of blood glucose (SMBG) or continuous glucose monitoring (CGM) and HbA1c 1.
From the Research
Utility of Hemoglobin A1c (HbA1c) in Severe Anemia
- HbA1c is a widely used marker for assessing glycemic control in diabetic patients, but its utility is limited in patients with severe anemia 2, 3.
- Severe anemia can lead to a shortened lifespan of erythrocytes, resulting in falsely low HbA1c values, making it a poor marker for glycemic control in these patients 2.
- Studies have shown that anemia, particularly iron deficiency anemia, can affect HbA1c levels, and correction of anemia can lead to changes in HbA1c values 3.
- HbA1c is not a reliable marker for glycemic control in patients with hemolytic anemia, and other measures such as fructosamine and 1,5-anhydroglucitol may be more suitable 4, 5.
Limitations of HbA1c in Severe Anemia
- HbA1c has several limitations, including interference from hematologic abnormalities, such as anemia, which can affect its accuracy 4, 6.
- Glycemic variability and self-monitoring of blood glucose (SMBG) may be more important factors to consider in the treatment of diabetes, particularly in patients with severe anemia 6.
- The clinical relevance of HbA1c in reducing cardiovascular morbidity and mortality is still debated, and other markers such as glycated albumin (GA) and 1,5-anhydroglucitol (1,5-AG) may provide a more complete picture of glycemia 5, 6.