Limited Discriminatory Capacity of Continuous Glucose Monitoring in Prediabetes and Increased Diabetes Risk: A Cross-Sectional Study

Background and Objectives: To determine whether continuous glucose monitoring (CGM)-derived metrics can differentiate between normoglycemia, increased diabetes risk (FINDRISC+) and prediabetes and to assess whether CGM-derived metrics provide additional discriminatory information beyond conventional laboratory markers. Materials and Methods: In this cross-sectional study, 41 adults without diabetes were classified as normoglycemic controls (HbA1c < 5.7%, FINDRISC < 12), individuals at increased diabetes risk (HbA1c < 5.7%, FINDRISC ≥ 12), or individuals with prediabetes (HbA1c 5.7–6.49%). All participants underwent 14-day CGM. Mean interstitial glucose, glycemic variability (SD, CV) and time in, above and below range (TIR, TAR, TBR) were analyzed. Group differences were assessed using ANOVA or non-parametric tests; correlations were evaluated using Pearson analysis. Results: HbA1c differed significantly across groups (F = 17.62; p < 0.001). Among CGM metrics, only mean interstitial glucose differed (F = 3.54; p = 0.039), driven by higher values in the prediabetes group. Glycemic variability and time-based metrics did not differ significantly. Substantial overlap was observed between the increased risk and prediabetes groups. No significant correlation was found between HbA1c and mean CGM glucose (r = 0.164; p = 0.30). Conclusions: In this exploratory cohort, short-term CGM-derived metrics provided limited additional discriminatory information beyond conventional laboratory markers and clinical risk assessment. Larger prospective studies are needed to determine the discriminatory and predictive value of CGM in early metabolic risk states.