Clinically useful estimates of insulin sensitivity during pregnancy - Validation studies in women with normal glucose tolerance and gestational diabetes mellitus

OBJECTIVE - We examined whether selected indexes of insulin sensitivity der ived from an oral glucose tolerance test (ISOGTT) or fasting glucose/insuli n levels (ISQUICKI and ISHOMA be used to predict insulin sensitivity in wom en before and during pregnancy, RESEARCH DESIGN AND METHODS - A 2-h euglycemic-hyperinsulinemic clamp (5 mm ol/l glucose, 40 mU . m(-2) . min(-1) insulin) and a 120-min oral glucose t olerance test (75 load pregravid, 100 g pregnant) were repeated on 15 women (10 with normal glucose tolerance [NGT] and 5, with gestational diabetes m ellitus [GDM]) pregravid and during both early (12-14 weeks) and late (34-3 6 weeks) pregnancy. An index of insulin sensitivity derived from the clamp was obtained from glucose infusion rates adjusted for change in fat-free ma ss and endogenous glucose production measured using [6,6-H-2(2)] glucose. RESULTS- Univariate analysis using combined groups and periods of pregnancy resulted in significant correlations between ISclamp and ISOGTT (r(2) = 0. 74, P < 0.0001), ISQUICKI (r(2) = 0.04 P < 0.0001), and ISHOMA (r(2) = 0.53 , P < 0.0001). The ISOGTT provided a significantly better correlation (P < 0.0001) than either ISQUICKI or ISHOMA Multivariate anal is showed a signif icant group effect (p < 0.0003) on the prediction model, and separate equat ions were developed for the NGT (r(2) = 0.64, P < 0.0001) and GDM (r(2) = 0 .85, P < 0.0001) groups. When subdivided by period of pregnancy, the correl ation between ISCLAMP and ISOGTT pregravid was r(2) = 0.63 (P = 0.0002), du ring early pregnancy was r(2) = 0.80 (p < 0.0001) and during late pregnancy was r(2) = 0.64 (P = 0.0002), CONCLUSIONS - Estimates of insulin sensitivity from the ISOGTT during pregn ancy were significantly better than from fasting glucose and insulin values . However, separate prediction equations are necessary for pregnant women w ith NGT and women with GDM.