Table 4

Strengths and limitations of using A1c for diabetes mellitus diagnosis

StrengthsLimitations
Reflects chronic hyperglycemia, providing global index of glycemic exposure (tracks well over time)
Less biological (day-to-day) variability compared with single fasting or 2-h glucose (26,31,32)
Eliminates need for fasting or timed samples
Unaffected by acute illness or recent activity (e.g., physical activity) (30)
Already used as a guide to adjust diabetes mellitus treatment (33)
Laboratory methods are well standardized in the U.S. and some other countries (33)
More robust predictor of complications than fasting blood glucose (18,20)
Certain conditions interfere with the interpretation of results (18,29,33) (www.ngsp.org), including hemoglobin traits and alterations in red cell turnover (e.g., hemolytic anemia, recent transfusion, pregnancy, loss of blood)
Lack of assay standardization in many parts of the world
Cost and lack of availability in resource-poor areas