Use of glycosylated hemoglobin in diagnosin pre-diabetes and diabetes in patients with hyperthyroidism

Glycosylated hemoglobin (HbA(1c)) >= 6.5% proposed as one of the criteria for the diagnosis of diabetes in the American Diabetes Association (ADA), 2010. For next year, the World Health Organization (WHO) 2011 guidelines recommended HbA lc as a criterion for diagnosising of diabetes. But the study of HbA(1c) as a standard for screening and the diagnosis of diabetes for patients with hyperthyroidism is rare. Abnormal glucose tolerance is common in patients with hyperthyroidism. In the late fasting state and postprandial state, hyperthyroidism leads to increased Cori cycle activity; in the fasting state, hyperthyroidism leads to an enhanced demand for glucose. After the diagnosis of hyperthyroidism, an oral glucose tolerance test was performed. In 508 hyperthyroid patients, were matched for age, fasting blood glucose, 2-hour postglucose load plasma glucose, and hemoglobin A1c. Our study showed that the prevalence of glucose intolerance in hyperthyroid state was 39.1% [impaired pre-diabetes (IGR) 35.6% and diabetes mellitus (DM) 3.5%]. HbA(1c) testing has the advantages of preanalytic stability, greater clinical convenience, and assay standardization. The diagnostic cut-off point of HbA(1c) >= 6.5% misses a substantial number of patients with hyperthyroidism accompany abnormal glucose tolerance. How to reduces the risk of systematic bias inherent in HbA(1c) testing alone. The results show that the diagnostic cut-off point of HbA(1c) of IGR in patients with hyperthyroidism was 5.4%, where the sensitivity was 55.9% and the specificity was 64.39%. The diagnostic cut-off point of HbA(1c) for DM in patients with hyperthyroidism was 5.5%, where the sensitivity was 79.71% and the specificity was 73.16%. HbA(1c) reflects the different glucose metabolic status in patients with hyperthyroidism, and the diagnostic cut-off points of HbA(1c )for screening pre-diabetes and DM are 5.4% and 5.5%, respectively.