Minimal Model–Derived Insulin Sensitivity Index Underestimates Insulin Sensitivity in Black Americans

OBJECTIVE: To examine the ethnic differences in insulin sensitivity (S(I)) as measured by the minimal model approach (S(I)-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: S(I)-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 S(I) measured by EHC (0.028 ± 0.012 vs. 0.035 ± 0.019 [dL/min]/[μU/mL]; P = 0.18). CONCLUSIONS: S(I)-MM systematically underestimates S(I) in BA when compared with NHW. These findings suggest that studies inferring lower S(I) in BA based on FSIVGTT and S(I)-MM should be interpreted cautiously.