Continuous glucose monitoring (CGM) provides detailed metrics for evaluating hypoglycemia risk in individuals with type 1 diabetes mellitus (T1DM). Time below range (TBR), which reflects the proportion of glucose readings below predefined thresholds, is commonly used to assess hypoglycemia exposure. A study published in Diabetes Care evaluated whether baseline CGM-derived TBR metrics can identify individuals at risk for severe hypoglycemia during follow-up.

The analysis combined data from six clinical trials and included 1,433 participants with T1DM. Median participant age ranged from 4 to 43 years across trials. Women represented 50% to 62% of participants, and 83% to 96% were White. Baseline TBR metrics were categorized as TBR level 1 (TBR1), defined as glucose levels below 70 mg/dL, and TBR level 2 (TBR2), defined as glucose levels below 54 mg/dL. Statistical analyses included Wilcoxon rank sum tests and Spearman correlations, with additional evaluation using receiver operating characteristic analysis.

Participants who experienced severe hypoglycemia during follow-up had slightly higher baseline TBR values. Median TBR2 was 0.41% in those with severe hypoglycemia compared with 0.32% in those without (P=0.022). Median TBR1 values were 2.58% versus 2.23%, respectively (P = 0.044). Baseline median TBR2 values ranged from 0.1% to 0.7%, while TBR1 ranged from 1.2% to 4.1% across trials.

Predictive performance was limited. For TBR2, sensitivity declined from 48.9% at a 1% threshold to 18.2% at a 5% threshold, while specificity ranged from 75.9% to 95.0%. For TBR1, sensitivity ranged from 81.8% to 44.3%, with specificity between 29.6% and 77.7%. Receiver operating characteristic analysis showed modest discrimination, with an area under the curve of 0.62 (95% CI 0.55-0.69) for TBR2 and 0.65 (95% CI 0.58-0.71) for TBR1. These findings indicate limited predictive value of baseline CGM TBR metrics for severe hypoglycemia risk.