Aim: HbA1c is recommended as a diagnostic criterion for diabetes in clinical practice guidelines for type 2 diabetes in 2011 (10). Although there have been several reports that compared HbA1c-based diagnosis for diabetes with glucose-based diagnosis in Koreans, it is thought that larger epidemiological studies are required to confirm the association of HbA1c and FPG for diagnosis of diabetes for the Korean population. We conducted this study to examine the relationship between FPG and HbA1c levels measured for diagnosis of diabetes and assess the differences in FPG and HbA1c values according to the HbA1c-based and FPG-based diagnosis of diabetes recommended from the ADA in the recent Korea National Health and Nutrition Examination Survey (KNHANES).
Methods: KNHANES, conducted periodically by the Korea Centers for Disease Control and Prevention and initiated in 1998, designed to provide comprehensive information of Korean on health status, health behavior, and nutritional status. Data from second (2011) years KNHANES V (fifth) which samplings include HbA1c over 10 years old men and women and fasting blood glucose were used in this cross-sectional analysis. From an initial total of 8518 men and women, 6066 persons (2677 men and 3389 women), with HbA1c and fasting glucose data and without diabetic medications, were evaluated. From 6066 persons, 1585 were excluded for several reasons. Baseline characteristics are presented as means for continuous variables, and proportions for categorical variables. The association of fasting blood glucose and HbA1c was examined using linear regression models.
Results: We found the results of linear regression analysis in the study population and in the subjects with diabetes by FBS criteria only. FPG 100 mg/dl, predicted HbA1c 5.75% in the study population and 5.76 in the subjects with diabetes by FBS criteria only respectively. FPG 126 mg/dl also predicted HbA1c 6.4 and 6.44%. However, in the subjects with diabetes by HbA1c criteria only, FPG 100 mg/dl, predicted HbA1c 6.49%, FPG 126 and 130 mg/dl, and predicted HbA1c 7.14 and 7.24% respectively.
Conclusions: This study is the first epidemiological report showing that an association between HbA1c and FPG levels for the diagnosis of prediabetes and diabetes is consistent with ADA recommendations in over 19 years old Korean population without diabetic medications. This conclusion requires further study to compare the characteristics of individuals with newly diagnosed diabetes by each only HbA1c- and only FPG-based diagnostic criteria and large-scale longitudinal study to assess the relation of HbA1c to incident diabetic retinopathy.