Repeatability of the hyperglycaemic clamp for assessment of β-cell response and insulin sensitivity in horses.

BACKGROUND

The hyperglycaemic clamp has been used for measurement of insulin sensitivity (IS) but not for measurement of β-cell response in the horse. However, the repeatability of this test has not been reported for horses.

OBJECTIVES

To determine the repeatability and reliability of measures for IS and β-cell response to glucose using the hyperglycaemic clamp in horses.

STUDY DESIGN

Repeated measures, longitudinal study.

METHODS

Six healthy Standardbred mares underwent a 120-min hyperglycaemic clamp on two occasions with a 10-day washout period. Indices of repeatability and reliability were calculated from measures of IS and β-cell response to glucose derived from each hyperglycaemic clamp.

RESULTS

Measures of β-cell response to glucose, including area under the insulin response curve in the time interval 0-120 min and during steady state (60-120 min), as well as the mean insulin concentration during steady state had coefficient of variations (CV) of 9.5, 10.5 and 9.3 respectively and intraclass correlation coefficients (ICC) of 0.93, 0.93 and 0.95 respectively. The measure of glucose disposal (M) had lower CV (12.4) and ICC (0.71) compared to measure of IS (M/I-index; CV of 17.4 and ICC of 0.89).

MAIN LIMITATIONS

The study was conducted in a small number of horses.

CONCLUSIONS

The hyperglycaemic clamp is a diagnostic method for assessing β-cell response to intravenous glucose with high repeatability and reliability. Insulin sensitivity can be determined with the same test but the repeatability for these measurements is lower compared to the measurements for β-cell response.