Comparison between fasting plasma glucose and glycated hemoglobin A1c in diagnosis of type 2 diabetes mellitus

Objective To compare the value of fasting plasma glucose(FPG)and glycated hemoglobin A1c(HbA1c) in the diagnosis of type 2 diabetes mellitus(2DM).Methods Levels of FPG and HbA1c were measured in 188 subjects with suspected diabetes mellitus.The diagnosis of DM was made according to 1999 WHO diagnosis criteria for 2DM(FPG ≥ 7.0 mmol/L) or the new diagnostic criteria of American Diabetes Association for 2DM(HbA1c ≥ 6.5%).The diagnosis of 2DM using these two criteria was compared,and the diagnostic sensitivity,specificity and likelihood ratio of HbA1c were calculated using FPG as reference.Results There was significant difference in mean FPG level between 2DM diagnosed by FPG and HbA1c(P0.05) and no significant difference was seen between non-DM groups diagnosed by these two criteria(P0.05).For mean of HbA1c,there was no significant difference between the 2DM groups diagnosed by FPG and HbA1c(P0.05) and significant difference was seen between the non-DM groups diagnosed by these two criteria(P0.05).The diagnostic sensitivity,specificity and negative and positive likelihood ratios of HbA1c using FPG as reference were 100%,93%,0.00 and 14.29,respectively.Conclusions HbA1c has high sensitivity and specificity in diagnosing diabetes and is an ideal indicator for both the inclusion and exclusion of diabetes mellitus.