Art and Science of Laboratory Medicine

Art and Science of Laboratory Medicine

Monday, December 28, 2015

Limitations of Hemoglobin A1c

Hemoglobin A1c is the measurement of glycated hemoglobin and can aid in both the diagnosis and continued management of diabetes mellitus. Accurate glycosylated hemoglobin A1c (A1c) measurements are an essential part of decision making in the diagnosis and treatment of type 2 diabetes mellitus. Although national standards exist to eliminate technical error with A1c testing, multiple patient conditions can falsely decrease or elevate the A1c. In this review, we discuss the methods to measure A1c and the corresponding conditions that can affect the clinical utility of the test. Conditions that affect the A1c can be either those that impair erythrocyte production or alter the normal process of glycation. Some variation also has been associated with patient ethnicity and even with normal aging. We describe alternatives to A1c testing for the above clinical scenarios in an effort to make the practicing clinician aware of alternatives for glucose evaluation.

Main limitations:
  • Methods to Measure Hemoglobin A1c
  • Erythrocyte Production
  • Ethnicity and Hemoglobin Variants
  • Chemically Modified Hemoglobin
  • Altered Rate of Glycation
  • Aging

Click to enlarge the table.

Many factors exist that may affect a patient's A1c. When A1c and self monitoring blood glucose (SMBG) results do not correlate, it is especially important to consider these patient-specific factors. The 2015 American Diabetes Association (ADA) Standards of Care state that discrepancies between a patient's A1c and SMBG levels should warrant exploration of the reasons for these discrepancies. Considerations should include testing method, hemoglobinopathies, conditions affecting red blood cell turnover, chemically modified hemoglobin, altered rates of glycation, race, and age. If a healthcare provider decides A1c is unreliable in a particular patient, alternative strategies for assessment of glycemic control should include more frequent or different timing of SMBG and continued glucose monitoring, as recommended by the ADA. In addition, clinicians can consider evaluation of fructosamine, glycolated albumin, and 1,5-AG; however, there are no consensus guidelines for their use.

Read more:
Limitations of A1c Interpretation (Free registration to the site is needed)

Source: Medscape

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