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

Disposition index (DI) is an informative measure of β -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 R ² and for discrimination of DI-defined β -cell dysfunction by AUROC. Performance was compared with conventional glycemic metrics. RBI predicted continuous DI more accurately than conventional glycemic metrics, with LOO R ² of 0.43, Pearson r = 0.70, and Spearman ρ = 0.75. RBI30–180 performed similarly, with cross-validated R ² of 0.42, Pearson r = 0.72, and Spearman ρ = 0.75. RBI also discriminated DI-defined β -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 β-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 β-cell compensation and support further validation of RBI in extended or CGM-augmented OGTT settings.