Monitoring Blood Glucose Levels

Key Differences Between Testing Methods

Laboratory-based serum A1c testing is considered the gold standard for assessing glycemic status and is used for both diagnosis and monitoring of diabetes, and must be performed using a method certified by the National Glycohemoglobin Standardization Program (NGSP) and standardized to the Diabetes Control and Complications Trial (DCCT) assay 1, 2
The American Diabetes Association recommends that laboratory serum A1c testing provides greater accuracy and precision compared to point-of-care testing, and typically performed in a clinical laboratory setting with standardized equipment 1, 3, 4
Point-of-care finger stick A1c testing provides immediate results during a clinical visit, allowing for timely treatment adjustments, but is generally less accurate than laboratory methods, with more potential for operator-related errors 2, 3
The American College of Clinical Endocrinologists recommends that only point-of-care A1c assays that are FDA-cleared for diagnostic use should be used for diagnosis 1

Hemoglobinopathies, such as sickle cell trait, can interfere with some A1c assays, and conditions affecting red blood cell turnover, such as hemolytic anemia, recent blood transfusion, or blood loss, can lead to falsely low or high results 1, 2, 5, 6
Pregnancy, particularly in the second and third trimesters, and end-stage kidney disease can also affect A1c accuracy 1, 2, 6
Erythropoietin therapy can interfere with A1c measurement, and race/ethnicity can affect A1c independent of glycemia, with African Americans potentially having higher A1c levels than non-Hispanic whites with similar glucose levels 1, 5, 6

The American Diabetes Association recommends using laboratory A1c testing for initial diagnosis of diabetes and routine monitoring of glycemic control, at least twice yearly for stable patients, and quarterly for those not meeting goals 1, 2, 5, 7
Point-of-care A1c testing can be used for more frequent monitoring between laboratory tests, in settings where immediate results would benefit clinical decision-making, and in remote locations where laboratory access is limited 3
Alternative testing methods, such as fructosamine or glycated serum protein testing, can be used when A1c cannot be reliably measured, and continuous glucose monitoring metrics, such as time in range, can provide additional information on glycemic control 2, 8, 9

The American College of Clinical Endocrinologists recommends using laboratory A1c testing for diagnosis of diabetes and primary assessment of glycemic control, and considering point-of-care testing as a supplement to laboratory testing, not a replacement 1, 3, 5
Be alert for marked discordance between measured A1c and plasma glucose levels, which may indicate A1c assay interference, and use alternative methods, such as fructosamine, glycated serum protein, or glucose-based criteria, in patients with conditions that affect A1c reliability 1, 2, 5, 8