Background: This study investigated the impact of age on the accuracy of glycated hemoglobin (HbA1c) for diabetes screening and explored the possible cause(s).
Materials and methods: Data from 3,050 Chinese participants 25-75 years of age without known diabetes in a population-based cross-sectional survey were analyzed. Diabetes was diagnosed by the oral glucose tolerance test (OGTT). The performance of HbA1c for detecting OGTT-defined diabetes in tertile groups (divided by age) was evaluated by the area under the curve (AUC) of the receiver operating characteristic curve (ROC). The effect of age on the difference in glucose levels between participants with and without diabetes and the impact of this difference on the performance of HbA1c were evaluated.
Results: In young (25-41 years old), middle-aged (41-53 years old), and old (55-72 years old) participants, the ROC AUC (95% confidence interval) of HbA1c for detecting OGTT-defined diabetes was 0.958 (0.915, 1.000), 0.891 (0.852, 0.930), and 0.861 (0.821, 0.901), respectively (P = 0.005). The difference of fasting plasma glucose between participants with diabetes and those without diabetes decreased with increasing age: 3.01 (2.80, 3.22) mmol/L, 2.90 (2.71, 3.09) mmol/L, and 2.33 (2.16, 2.50) mmol/L in the three consecutive age groups, respectively. A similar pattern was found in 2-h postprandial plasma glucose. The impact of age on the diagnostic power of HbA1c diminished after data were rearranged to artificially increase the difference between participants without diabetes and those with diabetes.
Conclusions: The accuracy of HbA1c for detecting OGTT-defined diabetes declines with age. This is largely due to the decreased separation in glycemic levels between participants with diabetes and without diabetes in the elderly.