Impact of glycated hemoglobin (HbA1c) on identifying insulin resistance among apparently healthy individuals

Aims: Insulin resistance has been implicated as a risk factor for metabolic disorders. Due to the clinical interest in insulin resistance, it is of great importance to develop a simple test that can be used in routine clinical settings for identifying insulin-resistant individuals in advance. Glycated hemoglobin (HbA1c) has been considered as a potentially good indicator of overall glycemic exposure and likely risk for long-term complications. Therefore, this study is designed to investigate the importance of HbA1c in predicting insulin resistance among apparently healthy at-risk German populations. Methods: The association between HbA1c and several surrogate markers of insulin resistance/sensitivity based on plasma glucose and insulin concentrations was analyzed by bivariate correlation along with multivariate linear regression and receiver-operating characteristic curve analysis among normal (NGT) and impaired glucose tolerance (IGT) individuals (n = 3578 aged >18 years) in Germany. Results: Spearman’s correlation coefficients showed that HbA1c had a significant association with insulin resistance/sensitivity markers in both NGT and IGT individuals and that this was stronger in the younger age group (<50 years) (rho = 0.410 with HOMA-IR, rho = −0.379 with the Matsuda index). Moreover, the ROC curve also showed that the HbA1c occupied a significant area under the curve (0.731 with 95% CI 0.661–0.801) and that the cutoff point for estimating insulin resistance corresponded to 5.8% (40 mmol/mol) with 34% sensitivity and 80% specificity. Conclusion: From this study, it could be concluded that HbA1c may be a clinically useful and simple index for predicting the concomitant presence of insulin resistance and dysglycemia among apparently healthy, young (<50 years) German populations. © 2017, Springer-Verlag Berlin Heidelberg.