title: Evaluation of proposed oral disposition index measures in relation to the actual disposition index.
abstract: Aims While the disposition index provides a useful measure of B-cell function, its calculation requires the performance of a frequently sampled intravenous glucose tolerance test (FSIVGTT). Recently, the demonstration of a hyperbolic relationship between indices of insulin secretion and insulin sensitivity derived from the oral glucose tolerance test (OGTT) has led to the introduction of two novel OGTT-based measures of B-cell function analogous to the disposition index: (i) the insulin secretion-sensitivity index-2 (ISSI-2) (defined as the ratio of the area-under-the-insulin-curve to the area-under-the-glucose curve, multiplied by the Matsuda index) and (ii) insulinogenic index (IGI)/fasting insulin. However, neither of these two measures has been directly compared with the disposition index. Methods Two hundred and thirteen non-diabetic children (122 boys, 91 girls) underwent both OGTT and FSIVGTT, allowing for the calculation of ISSI-2, IGI/fasting insulin and the disposition index. Results ISS1-2 and IGI/fasting insulin were strongly correlated with each other (r = 0.82, P < 0.0001). Both measures correlated with the disposition index, with ISSI-2 showing a modestly stronger association (ISSI-2: r = 0.24, P = 0.0003; IGI/fasting insulin: r = 0.21, P = 0.0022). Standardized linear regression analyses confirmed that the relationship between log ISSI-2 and the disposition index (standardized regression coefficient = 0.224, P = 0.001) was stronger than that between log IGI/fasting insulin and the disposition index (standardized regression coefficient = 0.166, P = 0.015). Conclusions The OGTT-derived measures ISSI-2 and IGI/fasting insulin exhibit modest correlations with the disposition index. These relationships require further assessment in other patient populations.
authors.affiliation: Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto, ON, Canada. rretnakaran@mtsinai.on.ca
authors.forename: R
authors.initials: R
authors.lastname: Retnakaran
authors.forename: Y
authors.initials: Y
authors.lastname: Qi
authors.forename: M I
authors.initials: MI
authors.lastname: Goran
authors.forename: J K
authors.initials: JK
authors.lastname: Hamilton
mesh_terms: D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism*; D002648:Child; D003920:Diabetes Mellitus / Q000175:diagnosis*; D005215:Fasting; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D007333:Insulin Resistance; D000078790:Insulin Secretion; D016014:Linear Models; D008297:Male; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity
chemical_list: D001786:Blood Glucose; D007328:Insulin