A Product of Fasting Plasma Glucose and Fasting Plasma Insulin : Simplified

Although every clinician hopes to diagnose type 2 diabetes in the earliest stages, the United Kingdom Prospective Diabetes Study (UKPDS) revealed that 50% of diabetic complications are present upon the diagnosis of diabetes, even with a fasting plasma glucose (FPG) of 6.1 mM/L. This emphasizes the need for diagnosing diabetes in the earliest stages of insulin resistance, before complications such as dyslipidemia and coronary artery disease occur. Diagnosing insulin resistance can be difficult in busy clinical practices. Euglycemic clamp studies, intravenous glucose tolerance tests (IVGTT), the homeostasis model assessment (HOMA), and the quantitative insulin sensitivity check index (QUICKI) were developed to facilitate diagnosis; however, they are impractical for the clinician. Using the insulin-to-glucose ratio has long since proved unreliable. Thus, a simple method to determine insulin resistance is needed. My colleagues and I conducted 2 studies to determine an insulin sensitivity index (ISI). In the first study, the FPG was multiplied by the fasting plasma insulin (FPI), a common denominator in HOMA and its variations, to determine the ISI in 44 patients with impaired glucose tolerance (IGT), in 53 patients with type 2 diabetes mellitus, and in 41 healthy subjects.The validity and reliability of FPG x FPI was tested by comparison with the ISI, as determined by IVGTT in 26 type 2 diabetic patients, before and after treatment with glyburide or metformin. There were 78 pairs of values. The mean ISI was 100 (±7) in subjects with IGT, 217 (±19) in patients with type 2 diabetes, and 34 (±2) in healthy research subjects (IGT versus normals, P<.001; type 2 diabetes versus normals, P<.0005; and type 2 diabetes versus IGT, P<.001). Linear regression analysis between FPG x FPI and ISI as calculated by IVGTT minimal model showed a highly significant correlation (r = -0.53, P<.00005). We concluded that FPG x FPI could be used to reliably diagnose insulin resistance in clinical practice. Patients were treated with metformin or glyburide at baseline. After treatment, the product of FPG x FPI decreased in patients who received metformin, indiPROCEEDINGS