15 They showed that lowest correlations were seen in the normal weight group, the highest in the obese group, and I-AUC was the most useful estimate in all weight groups (r = 0.69 to 0.72). In the HIV nondiabetic population, I-AUC also had the highest correlation coefficient with SSPG at 0.78 compared to other surrogate estimates.33 Similarly, in this study we showed that highest correlations

between the surrogate estimates and SSPG occurred in the obese HCV patients and that I-AUC had the highest correlation across normal and overweight groups in addition to having a high correlation in the obese group (r > 0.6). Insulin resistance is impacted by ethnicity. African Americans and Latinos have higher degrees of insulin resistance than whites.14, 17, 34 It has been shown that estimated indices of insulin resistance derived from OGTT are less likely to detect differences Selleckchem Cyclopamine among ethnic groups than the directly measured indices.16 Chiu et al. compared Matsuda index and Stumvoll index to hyperglycemic clamp in 105 glucose tolerant subjects in four ethnic groups: Asian, Caucasian, Mexican-Americans, and African Americans. They concluded that there were significant ethnic differences in directly measured insulin AG-014699 datasheet sensitivity and that Asians were most insulin resistant and Caucasians were most insulin sensitive. Although the estimated indices correlated with directly measured indices

(ranging from r = 0.30 to 0.52), the estimated indices did not accurately reflect the variation observed by the measured indices among different ethnic groups.16 In our study, we also found a significant correlation between estimated indices derived from OGTT and direct measures of insulin resistance, but these correlations varied between different ethnic groups. For example, whereas the correlation between Stumvoll index and SSPG was −0.35 among whites, this correlation increased to −0.66 among Latinos. I-AUC however, correlated consistently with SSPG among all ethnic groups. In this study we have highlighted limitations of HOMA-IR

in defining insulin resistance. First, HOMA-IR had a particularly low correlation (r = selleck 0.39) with SSPG in the normal weight group and accounted for only 15% of variability in SSPG in this group. Second, the most commonly cited HOMA-IR cutoff values for insulin resistance have high misclassification rates and even at HOMA-IR > 3, over one-third of patients were misclassified. In addition, degrees of obesity impacted the rate of false positivity of HOMA-IR cutoff values. Overweight subjects were particularly likely to be misclassified having a nearly four times higher odds of false positivity for insulin resistance compared to the normal weight group independent of ethnicity. Obesity has been associated with increased insulin secretion,35 decreased insulin clearance,36 and increased insulin resistance.