The Width–Delay Index: a Glucose-Only OGTT Metric for Assessing Insulin Resistance
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Background
Insulin resistance is a core pathophysiologic feature of metabolic disease, but its reference-standard assessment by steady-state plasma glucose (SSPG) testing is procedurally demanding and labor-intensive, limiting use in routine clinical care and large-scale research. Because OGTT glucose profiles are widely available, we aimed to develop a glucose-only metric to characterize dynamic glucose responses and estimate SSPG-measured insulin resistance.
Methods
We developed the Width–Delay Index (WDI), a glucose-only OGTT metric integrating relative exposure width, delayed exposure timing, and glycemic floor. In a dataset of 32 subjects with 16-point venous OGTT profiles and paired SSPG measurements, WDI performance was assessed using leave-one-out cross-validation (LOOCV) for SSPG prediction, together with insulin-resistance discrimination and sparse-sampling robustness analyses.
Results
The 15–120 min OGTT window yielded the strongest WDI performance. WDI15–120 predicted SSPG with LOOCV R 2 =0.57 (95% CI, 0.27–0.77), Pearson r = 0.77, and Spearman ρ = 0.74. WDI15–120 outperformed standard OGTT glucose measures and insulin-derived indices, including HOMA-IR, Matsuda index, and disposition index. WDI15–120 also discriminated insulin-resistant from insulin-sensitive subjects with AUROC = 0.969. When recalculated from conventional 5-point OGTT sampling, WDI15–120 retained substantial performance, with LOOCV R 2 = 0.41 and AUROC = 0.945.
Conclusions
WDI provides a simple, glucose-only, physiologically interpretable approach for estimating SSPG-measured insulin resistance from OGTT glucose dynamics.
