Insulin Resistance and Microalbuminuria in Patients with Impaired Fasting Glucose versus Hemoglobin A1c-Defined Prediabetes

Objective. This study investigated differences among patients with impaired fasting glucose (IFG) and hemoglobin A1c (HbA1c)-defined prediabetes (A1c-PDM); we compared insulin resistance and the prevalence of microalbuminuria (MAU) in these individuals. Methods. A total of 982 patients with newly diagnosed PDM and 455 non-PDM healthy individuals were evaluated. Serum insulin, HbA1c, fasting plasma glucose (FPG), and urine albumin excretion (UAE) levels were measured. The homeostasis model assessment of beta-cell function (HOMA-B) and insulin resistance (HOMA-IR) was calculated. Results. MAU was more prevalent in patients with IFG than in those with A1c-PDM (13.2% versus 6.4%, p=0.003). Patients with MAU had significantly higher FPG than those with normoalbuminuria (99.8 mg/dL versus 97.1 mg/dL, p=0.008). However, there was no significant difference in HbA1c levels between the two groups. Patients with IFG had significantly higher HOMA-IR values than those with A1c-PDM (2.31 versus 2.04, p=0.009). In contrast, there was no significant difference in the HOMA-B between the two groups. After adjusting for potential confounders, UAE was significantly correlated with FPG, but not with HbA1c. An elevated FPG level >= 113 mg/dL led to a 2.1-fold increase in the prevalence of MAU (odds ratio, 2.107; 95% confidence interval, 1.010-4.193; p=0.015). However, an elevated HbA1c level >= 6.1% was not significantly associated with the prevalence of MAU. Conclusion. Patients with IFG may be at a greater risk of insulin resistance and possible progression to diabetic nephropathy than patients with A1c-PDM.