Does leukocytosis (elevated white blood cell count) affect Hemoglobin A1c (HbA1c) levels?

From the Guidelines

Hemoglobin A1c (HbA1c) can be affected by leukocytosis, leading to falsely low readings due to increased red blood cell turnover. This occurs because leukocytosis is often associated with a higher proportion of younger red blood cells in circulation, resulting in less time for glucose to attach to hemoglobin. The most recent and highest quality study, 1, recommends that HbA1c measurements in individuals with disorders that affect red blood cell turnover, such as leukocytosis, may provide spurious results and glucose testing will be necessary for screening, diagnosis, and management. Key points to consider include:

• Leukocytosis can lead to increased red blood cell turnover, resulting in falsely low HbA1c readings
• Alternative methods for monitoring glucose control, such as fructosamine levels or glycated albumin, may be considered in cases of leukocytosis
• Clinicians should interpret HbA1c results with caution in patients with known leukocytosis to avoid underestimating their actual glycemic control
• The relationship between HbA1c and leukocytosis is complex and may be influenced by various factors, including the severity of leukocytosis and the presence of other medical conditions. Therefore, clinicians should be aware of the potential for leukocytosis to affect HbA1c results and take this into consideration when interpreting test results and making treatment decisions.

From the Research

Hemoglobin A1c and Leukocytosis

• The relationship between hemoglobin A1c (HbA1c) and leukocytosis is not directly addressed in the provided studies 2, 3, 4, 5, 6.
• However, it is known that HbA1c levels can be influenced by various factors, including changes in red blood cell lifespan and globin chain structure 2.
• Leukocytosis, which is an increase in white blood cell count, can be associated with various conditions, including infections, inflammatory diseases, and hematological disorders.
• While there is no direct evidence to suggest that leukocytosis affects HbA1c levels, it is possible that underlying conditions that cause leukocytosis may also impact HbA1c levels indirectly.

Factors Affecting HbA1c Levels

• HbA1c levels can be affected by several factors, including:
  • Red blood cell lifespan and globin chain structure 2
  • Blood glucose levels 3, 4, 5, 6
  • Renal function and end-stage kidney disease 4, 5, 6
  • Use of certain medications, such as insulin and sulfonylureas 4
  • Age and chronic kidney disease 4

Alternative Metrics for Glycemic Control

• Continuous glucose monitoring (CGM) metrics, such as time in range (TIR), time below range (TBR), and time above range (TAR), can provide additional information on glycemic control beyond HbA1c levels 3, 4, 5, 6.
• Fructosamine levels can also be used as an alternative metric for glycemic control, particularly in patients with end-stage kidney disease 6.