To analyze in a population of persons with type 1 diabetes (PwT1D) ambulatory glucose profile (AGP) parameters – including glycemia risk index (GRI) – for six months after hybrid closed loop (HCL) initiation in a multisite out-of-hospital French center (CIRDIA). We calculated the percentage of people reaching glucose targets and determined a GRI threshold that could identify patients reaching targets.

This was a retrospective study conducted in the CIRDIA, a multisite (n=7) out-of-hospital HCL initiation center. AGP metrics for the 14 previous days were manually extracted from HCL platforms at initiation (M0), 3 ± 1 months (M3) and 6 ± 1 months (M6). PwT1D were considered as reaching efficacy and safety targets (EST) if time-in-range was > 70 %, GMI was < 7 %, time-below-range (TBR)^<70 was < 4 % and TBR^<54 was < 1 %. GRI was calculated and ROC analyses were performed to set a GRI threshold that could identify patients reaching EST.

Six-month data were available for 136 persons. The percentage of PwT1D reaching glucose targets at respectively M0, M3 and M6 were for EST: 6.6 %, 40.4 % and 39.7 %. GRI decreased from 56.0 ± 20.9 to 30.1 ± 14.1 and 30.6 ± 13.8. ROC analyses showed that the best GRI value to detect patients who reached EST was GRI <26. A threshold set at this level had very good specificity (92 %) and negative predictive value (93 %) to identify those who do need further intensive support with HCL.

Setting a GRI threshold at 26 could be helpful to detect with a single number, potentially automatically calculated by CGM platforms, PwT1D who require further support.