The euglycemic hyperinsulinemic clamp examination: variability and reproducibility

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Abstract
The aim was to examine the reproducibility of the euglycemic hyperinsulinemic clamp method. From a random population sample of 60-year-old clinically healthy men, 32 subjects with varying degrees of insulin sensitivity were recruited. Conventional 2-h clamp examinations were carried out at an interval of 2 weeks. Insulin was infused intravenously (priming for 10 min and thereafter 1.0 mU/kg body wt/min). Glucose was infused concomitantly aiming at a whole blood glucose of 5 mmol/L. The glucose infusion rate (GIR) was adjusted for body weight or fat free mass (FFM), the latter measured with dual-energy X-ray absorptiometry. During the final hour of each examination (60-120 min) the mean whole blood glucose concentrations were 5.06+/-0.15 and 5.09+/-0.17 mmol/L, respectively. Of the different time intervals studied, the glucose infusion rate during the final hour (GIR60-120) showed the highest correlation and lowest coefficient of variation (GIR60-120 adjusted by FFM: r=0.70, coefficient of variation=14.7%). Adjustment of GIR for weight instead of FFM underestimated insulin sensitivity in obese men. GIR60-120 adjusted for FFM tended to increase during the second examination. The measurement error was constant across all GIR. In summary, the euglycemic hyperinsulinemic clamp method has a coefficient of variation around 15%. The glucose infusion rate should be adjusted for fat free mass.