Minimal Model-Derived Insulin Sensitivity Index Underestimates Insulin Sensitivity in Black Americans.

OBJECTIVE To examine the ethnic differences in insulin sensitivity (SI) as measured by the minimal model approach (SI-MM) and the reference method, the euglycemic-hyperinsulinemic clamp (EHC). RESEARCH DESIGN AND METHODS In a prospective study design, thirty black Americans (BA) were age, sex, and BMI matched with non-Hispanic whites (NHW). Participants underwent frequently sampled intravenous tolerance test (FSIVGTT) and EHC on 2 separate days during a single visit. RESULTS SI-MM values were significantly lower in BA when compared with NHW (0.035 ± 0.025 vs. 0.058 ± 0.036 [dL/min]/[μU/mL]; P = 0.003). However, there were no ethnic differences in SI measured by EHC (0.028 ± 0.012 vs. 0.035 ± 0.019 [dL/min]/[μU/mL]; P = 0.18). CONCLUSIONS SI-MM systematically underestimates SI in BA when compared with NHW. These findings suggest that studies inferring lower SI in BA based on FSIVGTT and SI-MM should be interpreted cautiously.