The Recovery-Burden Index for Assessing Beta-Cell Function from OGTT Glucose Profiles

Disposition index (DI) is an informative measure of {beta}-cell function adjusted for insulin resistance, but its assessment is procedurally demanding, requiring dynamic testing with timed sampling and insulin or C-peptide-based estimation of insulin sensitivity and secretion. A simple glucose-only metric derived from the oral glucose tolerance test (OGTT) could provide a practical approach to estimating DI. We developed the Recovery-Burden Index (RBI), a glucose-only geometric metric that quantifies post-peak glucose recovery relative to total glucose excursion during OGTT. Using densely sampled venous OGTT profiles with measured DI, RBI was evaluated for prediction of continuous DI by leave-one-out (LOO) cross-validated R2 and for discrimination of DI-defined {beta}-cell dysfunction by AUROC. Performance was compared with conventional glycemic metrics. RBI predicted continuous DI more accurately than conventional glycemic metrics, with LOO R2 of 0.43, Pearson r = 0.70, and Spearman{rho} = 0.75. RBI30-180 performed similarly, with cross-validated R2 of 0.42, Pearson r = 0.72, and Spearman{rho} = 0.75. RBI also discriminated DI-defined {beta}-cell dysfunction, with AUROC values of 0.90 for RBI and 0.91 for RBI30-180. Reduced sampling schedules preserved much of the RBI signal, whereas truncation at 120 min attenuated continuous DI prediction, supporting the contribution of late recovery-phase information. RBI extracts {beta}-cell-relevant information from the OGTT glucose profile using a single transparent glucose-only index. These findings highlight post-peak recovery as a key feature for estimating DI-associated {beta}-cell compensation and support further validation of RBI in extended or CGM-augmented OGTT settings.