A novel disposition index without insulin is an earlier and sensitive predictor of type 2 diabetes than current diagnostic criteria

Abstract

Aims: Early identification of individuals at risk for type 2 diabetes (T2D) is essential for prevention. We evaluated a novel model-derived disposition index without insulin (mDI-woI), which requires only glucose values from a three time-point oral glucose tolerance test (OGTT: 0, 60, 120 min).

Methods: Among 5,742 healthy Koreans (age 51.2 ± 8.6 years, BMI 24.5 ± 3.1 kg/m²) followed biennially for up to 14 years with repeated OGTTs, we compared baseline mDI-woI with current diabetes biomarkers and the oral disposition index (oDI) using AUC-ROC analyses.

Results: mDI-woI and mean OGTT glucose (mean G) showed the strongest prediction for incident T2D (AUC = 0.79 each), outperforming fasting plasma glucose (0.67), 1 h-PG (0.77), 2 h-PG (0.72), HbA1c (0.71), and oDI (0.68; all P < 0.001). In individuals who progressed to T2D, baseline mDI-woI, mean G, and 1-PG exceeded their thresholds while fasting and 2 h glucose were still below prediabetes cutoffs, indicating earlier risk detection. Moreover, the novel marker mDI-woI is the earliest one, 4 years earlier than mean G and 4.5 years earlier than 1 h-PG, the next two earliest.

Conclusions: Using only three glucose measurements without measuring insulin, mDI-woI provides a simple, sensitive, and clinically practical early marker that outperforms current diabetes criteria for predicting T2D progression, with strong potential for large-scale studies.

Keywords: Diabetes criterion; Disposition index; Insulin resistance; Oral glucose tolerance test; β-cell function.