correlation study of some methods used for insulin sensitivity assessment: the Egyptian experience

Various surrogate methods for the quantification of insulin sensitivity have been proposed. A comparative evaluation is lacking and is relevant for the standardization of investigative methods and comparability of results. A gold standard in measuring insulin sensitivity is the minimal model derived estimates of insulin sensitivity, but this method is difficult to apply in large studies. Therefore, indirect indices of insulin sensitivity were proposed, namely I, In [I], 10[4] [I x G], I/G, HOMA-IR, In [HOMA-IR], QUICKI, AIR, and HOMA-beta cell. The aim of the present study was to compare these simple indices with data from the MINMOD. Forty Egyptian subjects of whom 15 were obese and 25 were nonobese. All subjects underwent an FSIGT. Plasma glucose was determined and serum insulin was measured. The insulin sensitivity, SI was calculated with the MINMOD program. HOMA IR, beta cell function and QUICKI were calculated. In [HOMA-IR] correlated best with the MINMOD-derived SI [r = -0.401, P = 0.010]. This was followed by In [I] and QUICKI which were equally correlated with SI [r = -0.389, P = 0.013 and r = 0.388, P = 0.013, respectively]. This was followed by I/G and HOMA-IR which correlated better with the MINMOD-derived SI than 10[4] / [Insulin x G] and I, respectively [r -0.352, P = 0.026 and r = -0.350, P = 0.027 versus r = 0.343, P = 0.030 and r = -0.343, P = 0.030, respectively]. AIR and HOMA-beta cell did not show any statistically significant correlation with the MINMOD-derived SI. In both obese and nonobese subjects HOMA-IR showed a highly significant negative correlation with QUICKI [r = -0.875, P = 0.000 and r = -0.890, P = 0.000, respectively]. Also, In [HOMA-IR] showed a highly significant negative correlation with QUICKI in both obese and nonobese subjects [r = -0.968, P = 0.000 and r = -0.947, P = 0.000, respectively]. Fasting insulin-derived measures of insulin sensitivity proposed are relatively crude methods for the quantification of insulin sensitivity in comparison to the Minimal Model analysis of the FSIVGTT and are, therefore, of limited value for the assessment of the metabolic status of an individual patient. When used in epidemiologic studies, fasting insulin alone, or the widely used HOMA or QUICKI perform at least as surrogate measures of insulin sensitivity or means for the identification of individuals with the metabolic syndrome in the general population

Evaluation of simpler methods for the assessment of insulin sensitivity in Egyptians

Aim: A number of insulin sensitivity indices are frequently used. These are fasting insulin [I], 40/1, HOMA-IR, n[HOMA], 1/HOMA, I/G, and G/l, where G and I are the fasting glucose, and insulin concentrations, respectively. To test the validity of these simple indices in Egyptians, their values were computed and correlated with the MINMOD-derived S1 value. Subjects and The present study was carried out on 40 Egyptian subjects [15 obese and 25 nonobese]. The weight and height were measured from which the BMI was calculated. Skinfold thickness was measured from the biceps, triceps, subscapular and supra-iliac region. The body fat content was calculated. Waist and hip circumference were measured from which waist/hip ratio was calculated. All subjects underwent a 75 g OGTT followed, at least 7 days later, by an FSIVGTT. Plasma glucose was determined and serum insulin was measured by EASIA. Insulin sensitivity, S1, and glucose effectiveness, SG, were calculated with the MINMOD program. The insulin sensitivity indices were also calculated from the fasting insulin [I], fasting glucose [G], 40/I, HOMA-IR, In [HOMA], 1/HOMA and G/l. A significant correlation was found between S1, and I, 40/I, HOMA-IR, in [HOMA], 1/HOMA, I/G and G/l. Ln [HOMA], G/l, 40/I and HOMA-IR correlated better with MINMOD S1, than I, 1/HOMA, I/G and G. Conclusions: These simple S1 indices give only approximate values which cannot be counted upon in all cases. Further studies are needed to characterize the validity of these simple indices in terms of the factors responsible for insulin sensitivity, to validate these measures in different populations and to clarify the differences between different studies