From the Research
Microcytosis can affect Hemoglobin A1c (HbA1c) levels, potentially causing falsely elevated readings. Microcytosis, characterized by smaller than normal red blood cells (often measured as low MCV or mean corpuscular volume), can occur in conditions like iron deficiency anemia, thalassemia, and certain hemoglobinopathies 1, 2, 3. When red blood cells are smaller, there is a higher ratio of cell surface area to volume, which can lead to an increased proportion of older red blood cells in circulation. Since HbA1c measures the percentage of hemoglobin that has glucose attached to it (glycation), and older red blood cells have had more time for glycation to occur, this can result in artificially higher HbA1c values that don't accurately reflect average blood glucose levels. This effect is particularly notable in patients with hemoglobinopathies like thalassemia.
Some key points to consider in the evaluation of microcytosis include:
- The most common causes of microcytosis are iron deficiency anemia and thalassemia trait 2
- Serum ferritin measurement is the first laboratory test recommended in the evaluation of microcytosis 2
- The presence of microcytosis can be assessed using automated measurements of red blood cell microcytosis and hypochromia, such as those provided by the H*1 hematology analyzer 4
- The microcytic-hypochromic ratio can be useful in differentiating iron deficiency from beta-thalassemia trait 4
For patients with known microcytosis, healthcare providers should consider using alternative methods to monitor glycemic control, such as fructosamine testing, glycated albumin, or more frequent blood glucose monitoring, to ensure accurate assessment of diabetes management. Additionally, the relationship between HbA1c and mean blood glucose is influenced by variation in red blood cell survival, even in hematologically normal individuals 5.
Overall, microcytosis can have a significant impact on HbA1c levels, and healthcare providers should be aware of this potential effect when interpreting HbA1c results in patients with microcytosis.