Hjelmesaeth et al. (1) have validated the use of seven oral glucose tolerance test (OGTT)-derived insulin sensitivity indexes against the euglycemic-hyperinsulinemic clamp technique in a Caucasian renal transplant population. We agree with the authors that the availability of more cost- and time-efficient surrogate estimates of insulin sensitivity than the euglycemic-hyperinsulinemic clamp would greatly benefit the design of future epidemiological studies investigating the role of insulin resistance in the extremely high incidence of diabetes and cardiovascular disease in renal transplant recipients (2,3). The authors found all seven insulin sensitivity indexes to correlate significantly with the euglycemic clamp. They concluded that an insulin sensitivity index based on glucose and insulin serum concentrations 2 h after the glucose challenge from the OGTT suffices best in renal transplant recipients. However, the routine performance of OGTTs to assess insulin sensitivity in renal transplant recipients is cumbersome, time-consuming, and frequently impossible in busy outpatient practices. McAuley et al. (4) recently suggested an insulin sensitivity index based on fasting serum insulin and triglyceride concentrations (Exp[2.63 − 0.28ln(insulin) − 0.3ln(TG)]) as a better predictor of insulin sensitivity than homeostasis model assessment (HOMA) in the general population. Insulin sensitivity indexes based on fasting parameters alone don’t have the drawback of interference with outpatient practices. For this reason, it would have been very interesting if the authors had included this insulin sensitivity index in their analyses to assess whether this measure correlates better with the results from the euglycemic-hyperinsulinemic clamp than with HOMA or even the insulin sensitivity indexes derived from the 2-h glucose and insulin concentrations of the OGTT.
Address correspondence to Aiko P.J. de Vries, Department of Medicine, Division of Nephrology, Groningen University Medical Center, P.O. Box 30.001, NL-9700 RB Groningen, The Netherlands. E-mail: email@example.com.