The value of HbA1c for diagnosing type 2 diabetes

Objective To compare the sensitivity and specificity of fasting plasma glucose(FPG),2 h post-load plasma glucose(2hPG) and glycated hemoglobin(HbA1c) in diagnosing type 2 diabetes in order to explore the value of HbA1c in diabetes diagnosis.Methods We selected 285 outpatients with risk factor for type 2 diabetes,including 158 males and 127 females,with the mean age of(48±11) years.All the subjects underwent oral glucose tolerance test(OGTT),and their HbA1c level was also measured.Results ① Based on the diabetes diagnosis criteria of WHO(1999),the subjects were divided into diabetes mellitus(DM) group(n=176),impaired glucose regulation(IGR) group(n=71),and normal glucose tolerance(NGT) group(n=38).The HbA1c level in the three groups tended to increase(P0.05).②Spearman correlation analysis demonstrated that HbA1c was positively correlated with FPG and 2hPG level determined by OGTT(r=0.72,0.59,P0.05).③ The optimal cut-point of HbA1c for diagnosing type 2 diabetes was 6.1%.HbA1c had higher diagnostic sensitivity than FPG,but lower than 2hPG.When HbA1c was≥6.5%,its diagnostic sensitivity was still lower than 2hPG.The diagnostic sensitivity of combined detection of FPG and HbA1c(≥6.5%) was greater than the diagnostic sensitivity of 2hPG.Conclusion HbA1c measurement is valid in diagnosing diabetes when OGTT is not available,but it should be combined with FPG detection.