CGM Time Above 140mg/dL Predicts Stage 3 Type 1 Diabetes Similarly to OGTT

Continuous glucose monitoring (CGM)–derived time above 140mg/dL (TA140) performed similarly to a 2-hour oral glucose tolerance test (OGTT) glucose value in predicting progression to stage 3 type 1 diabetes (T1D) among individuals with early-stage T1D, according to a study published online in The Journal of Clinical Endocrinology & Metabolism.

Investigators analyzed a combined dataset from 3 prospective studies that included 152 individuals with early-stage T1D who had baseline CGM, OGTT, and HbA1c measurements; 54 (36%) progressed to stage 3. Predictive performance was compared using areas under the curve, and progression risk was estimated with accelerated failure time (AFT) and Kaplan-Meier analyses.

For predicting stage 3 at 2 years, TA140 greater than 10% and 2-hour glucose greater than 140mg/dL had identical specificity (83%), negative predictive value (88%), and sensitivity (55%). In univariable AFT analyses, all CGM metrics tested were significantly associated with stage 3 at 5 years (all P ≤ .008), as were OGTT 2-hour glucose, glucose and C-peptide areas under the curve, and peak C-peptide (all P ≤ .021).

In multivariable AFT analysis, the investigators identified younger age, male sex, HbA1c of 5.7% or higher, TA140 greater than 15%, and 2-hour glucose greater than 140 mg/dL as strong predictors of faster progression to stage 3. Cumulative incidence curves for stage 3 were similar across those TA140, HbA1c, and 2-hour glucose thresholds. Among 406 longitudinal CGM assessments, median TA140 was 3.2% at stage 1, 8.6% at stage 2, and 17.2% at stage 3 (all pairwise P ≤ .024).

The authors, who described the cohort as the largest dataset of individuals with early-stage T1D, said the findings define CGM-derived TA140 criteria for the stages of T1D and show that TA140 performs similarly to a 2-hour OGTT value for predicting stage 3.

Source: Steck AK, Dong F, Pyle L, et al. CGM has similar predictive performance to OGTT for monitoring early-stage type 1 diabetes. J Clin Endocrinol Metab. Published online October 7, 2026. doi:10.1210/clinem/dgag394