Correlativity study of the glycosylated hemoglobin to evaluate diabetes mellitus and impaired glucose regulation

Objective To identify the optimal HbA1c threshold which as a diagnostic test for type 2 diabetes in middle-age adults.Methods This study included 1059 adults from one institution of higher learning.Without known diabetes who had an oral glucose tolerance test and HbA1c,serum biochemistry indicators were measured on the same day.Make use of receiver operating characteristics curve to detect optimal HbA1c threshold.Results(1)HbA1c levels with age increasing.Under the age of 30,the average of HbA1c is(5.2±0.3)%,while,at the age of 50-80,the average of HbA1c is(5.6±0.6)%.(2)According to ROC,the optimal cut-off point of HbA1c for the diagnosis of diabetes is 5.7%(sensitivity 66.7%,specificity 86.7%),this result mean that 66.7% of diabetic subjects show an HbA1c≥5.7%,while 10.6% NGT and 44.0% IGR subjects have an HbA1c≥5.7%.(3)Similarly,the optimal cut-off point of HbA1c for the diagnosis of IGR is 5.6%(sensitivity 55.8%,specificity 82.8%),this result mean that 56.0% of IGR subjects show an HbA1c≥5.6%,while 16.9% NGT and 73.3% NDD subjects have an HbA1c≥5.6%.(4)The risk factors of metabolic syndrome with HbA1c levels increasing.When HbA1c≥6.0% and HbA1c≥6.2%,there are two or more risk factors of metabolic syndrome in 85.7% NDD and 75% IGR subjects,respectively.Conclusions The optimal cut-off points of HbA1c for the diagnosis of diabetes and IGR is 5.7%,5.6%,respectively.If use the HbA1c 5.7% to separating NDD from NGT,about 10% NGT subjects will be diagnosed NDD.The risk factors of metabolic syndrome is increased obviously when HbA1c≥6.0%.