Joslin's Diabetes Deskbook, A Guide for Primary Care Providers, Updated 2nd Ed., Excerpt 2: Do You Know the Conditions that May Cause Inaccurate Results from the A1C Test?

Joslin's Diabetes Deskbook, A Guide for Primary Care Providers, Updated 2nd Ed., Excerpt 2: Do You Know the Conditions that May Cause Inaccurate Results from the A1C Test?
By Richard S. Beaser, M.D.


"... With respect to the testing methodology, when HPLC laboratory techniques are used to perform measurements, the number of things that can affect the test results is limited. Using this methodology, the most common factors that can affect A1C measurements are:

• Hemolytic anemias Carbamylated and acetylated hemoglobins (rare).
• "Fast" migrating hemoglobins, most commonly hemoglobins D, J, and N, can lower readings.
• Fetal hemoglobin greater than 25% interferes with hemoglobin A1c measurement and cannot be corrected for.
• True beta-thalassemia will interfere with some HPLC methods, but the patient has to be symptomatic at the time for the effect to be significant.
• Severe lipemia in some patients can interfere with measurements. Interference can be reduced by washing red cells and making an offline dilution to report out the A1C value
• Taking medications such as salicylates can have an effect, though rarely ..."