Measurement of insulin sensitivity in Type 2 diabetes mellitus: comparison between KITT and HOMA-%S indices and evaluation of their relationship with the components of the insulin resistance syndrome.

AIMS: The identification of alternative methods of the euglycaemic-hyperinsulinaemic clamp to estimate the insulin-sensitivity is a continuous challenge. The aim of the study was to evaluate the agreement between the short Insulin Tolerance Test (ITT) and the Homeostatic Model Assessment (HOMA), and their relationship with the components of the insulin resistance syndrome, in recently diagnosed Type 2 diabetic patients.
METHODS: Two hundred and forty-seven patients, aged 26-65 years, consecutively recruited, were studied. The subjects underwent the ITT and HOMA tests to calculate the K(ITT) and the HOMA-%S indices, along with the measurement of the components of the insulin resistance syndrome.
RESULTS: The correlation between K(ITT) and HOMA-%S was highly significant, but the correlation coefficient and the explained variance were rather low (r = 0.44, R(2) = 0.19, P-value < 0.0001) as well as the agreement among tertiles of the two indices (kappa = 0.26). The strength of the association was similar in subgroups of subjects defined by sex, type of hypoglycaemic therapy, presence of hypertension or antihypertensive therapy, fasting blood glucose, whereas it was better in obese compared with non-obese patients. Nonetheless, both K(ITT) and HOMA-%S correlated significantly with the components of the insulin resistance syndrome (P-value < 0.05-0.001).
CONCLUSIONS: The association between HOMA-%S and K(ITT) was significant but quite low. Therefore the two measures could not be considered interchangeable estimates of insulin sensitivity. However, as both indices showed significant associations with the components of the insulin resistance syndrome, probably they represent different metabolic aspects of the insulin resistance.