Estimation of fasting plasma glucose from HbA1c in diabetic patients at Srinagarind Hospital, Khon Kaen University

Abstract

Glycated hemoglobin (HbA_1C) has been measured to assess glycemic control in diabetic patients in the past 90-120 days and usually interpreted with fasting plasma glucose (FPG).   However, plasma glucose is related with diet and overnight fasting resulting in discordance of FPG and HbA_1C.  It has been reported that the estimated fasting plasma glucose (eFPG) based on HbA_1C value can be done with formula; eFPG = (28.7 x HbA_1C) – 46.7. American Diabetes Association (ADA) recommends this formula to estimate fasting plasma glucose in type 2 diabetic patients.  The aim of this study was to investigate eFPG and compare with FPG. Study was performed on 271 diabetic patients who attended diabetic clinic at Srinagarind Hospital, Faculty of Medicine, Khon Kaen University.  The FPG and eFPG values were 140 ± 52 mg/dL and 155 ± 42 mg/dL, respectively. FPG and eFPG are moderately correlated in all subjects (r = 0.66, P < 0.001), and in group with HbA_1C ≤ 7 % and HbA_1C > 7 %.  Statistical difference between FPG and eFPG was found in all subjects (P < 0.001) and in both subgroups.  In addition, 69 % of diabetic patients demonstrated more than 10 % bias between FPG and eFPG. The results imply that the assessment of glycemic control following FPG should be considered in conjunction with the eFPG and HbA_1c to avoid false hypoglycemia.

Keywords:  Estimated fasting plasma glucose,  HbA_1c,  Type 2 diabetic patients