Table 2.

Considerations related to the use and interpretation of laboratory measurements of glucose and HbA_1c

	Glucose	HbA1c
Cost	Inexpensive and available in most laboratories across the world	More expensive relative to glucose and not as widely available globally
Time frame of hyperglycemia	Acute measure	Chronic measure of glucose exposure over the past ∼2–3 months
Preanalytic stability	Poor preanalytical stability; plasma must be separated immediately or samples must be kept on ice to prevent glycolysis	Good preanalytical stability
Sample type	Measurement can vary depending on sample type (plasma, serum, whole blood) and source (capillary, venous, arterial)	Requires whole blood sample
Assay standardization	Assay is not standardized	Assay is well standardized
Fasting	Fasting or timed samples required	Nonfasting test; no patient preparation is needed
Within-person variability	High within-person variability	Low within-person variability
Acute factors that can affect levels	Food intake, stress, recent illness, activity	Unaffected by recent food intake, stress, illness, activity
Other patient factors that can affect test results	Diurnal variation, medications, alcohol, smoking, bilirubin	Altered erythrocyte turnover (anemia, iron status, splenectomy, blood loss, transfusion, erythropoietin, etc.), cirrhosis, renal failure, dialysis, pregnancy
Test interferences	Depends on specific assay: sample handling/processing time, hemolysis, severe hypertriglyceridemia, severe hyperbilirubinemia	Depends on specific assay: hemoglobin variants, severe hypertriglyceridemia, severe hyperbilirubinemia