HCL Systems Convey Superior Glucose Outcomes vs Other Diabetes Technologies

This new study among a patient population living with type 1 diabetes compared their outcomes according to their type of insulin pump therapy: sensor-augmented pump, predictive low-glucose suspend, and hybrid closed-loop (HCL).

Hybrid closed-loop (HCL) systems produced consistently better results for euglycemia, lower glycemic variability, and hypoglycemic risk vs sensor-augmented pump (SAP) therapy and use of a predictive low-glucose suspend (PLGS) algorithm among 136 adult patients living with type 1 diabetes in a new study.

Findings from this retrospective analysis were published in a new issue of Frontiers in Endocrinology, and they focused on outcomes seen among 3 groups of patients receiving care at Unit of Diabetology and Endocrinology in Fatebenefratelli-Sacco Hospital, in Milan, Italy, between December 2020 and June 2021. The HCL treatment group was the largest (n = 63), followed by those utilizing PLGS (n = 49) and SAP (n = 24) therapies. All of the patients received education on features of continuous subcutaneous insulin infusion (CSII) and measured their carbohydrate intake on a regular basis. For the duration of the study, they had an average of 1 visit every 4 months.

“The last 3 decades showed the emergence of innovative diabetes technologies aimed at improving outcomes and easing the burden of diabetes management,” the authors wrote. “The aim of this study was to evaluate the effectiveness of different categories of insulin pump in maintaining improved metabolic control in T1D subjects.”

Among the study participants—51% male, mean (SD) age of 47.3 (13.9) years—the mean (SD) time since diagnosis of their T1D was 25.6 (12.6) years. With crossover allowed in the study, the HCL group had the highest percentage of patients switch from multiple daily insulin injections to CSII (38.1%) compared with the crossover seen with the PLGS (28.6%) and SAP (20.8%) groups.

Demographic, biochemical, and anthropometric characteristics were similar between the groups, and hemoglobin A1C (HbA1C) did not significantly differ—although it was lowest in the participants using HCL systems. Patients in the HCL group had a mean (SD) baseline HbA1C of 7.2% (0.7%) compared with 7.3% (0.8%) and 7.6% (1.4%) seen in the PLGS and SAP groups, respectively. In addition, CSII use was longest in the PLGS group vs the SAP and HCL groups: 5.5 (4.5) vs 4.1 (2.3) and 3.7 (3.9) years, respectively.

Percentages of time in range (TIR; 70-180 mg/dL), time below range (TBR2, < 54 mg/dL; TBR1, < 70 mg/dL), and time above range (TAR1, > 180 mg/dL; TAR2, > 250 mg/dL) were evaluated for blood sugars. TIR showed a continual increase when moving from the SAP to the PLGS to the HCL group, with a majority of participants in the HCL group spending more than 70% of their TIR compared with 32.7% in the PLGS group and 20.2% in the SAP cohort. In addition, for the TBR2 measure, significant reductions were seen when comparing the SAP with the PLGS group and the SAP with the HCL group (P = .003).

Hyperglycemia exposure as indicated by TAR2 was reduced more when comparing the HCL group vs the SAP group (6.2%) than the HCL group vs the PLGS group (3.1%), and instances of severe hyperglycemia were significantly reduced in the HCL (–1.17%) and PLGS (–0.9%) groups vs the SAP group.

A positive correlation was seen, too, within the HCL group for increasing time spent in auto mode and more percentage of time spent in TIR (P = .009).

Because all of the study participants were shown to have consistently incorporated use of their automatic bolus insulin calculator feature, the study investigators were able to thoroughly compare outcomes among the categories of diabetes technology they evaluated. In addition, their findings echo previous research that shows greater percentage of TIR with use of an HCL system. They cite the lack of a control group as a limitation to wider generalizability of their findings.

“In conclusion, our study demonstrates that HCL and advanced HCL systems provide better glycemic control, compared to standard sensor-augmented pumps but also to suspend before low technology, allowing a higher percentage of time in the euglycemic range, lower glucose variability, and lower hypoglycemic risk,” the authors wrote. “These aspects point to a promising trend in improving quality of life and higher acceptance of CSII systems.”


Lunati ME, Morpurgo PS, Rossi A, et al. Hybrid close-loop systems versus predictive low-glucose suspend and sensor-augmented pump therapy in patients with type 1 diabetes: a single-center cohort study. Front Endocrinol (Lausanne). Published online April 14, 2022. doi:10.3389/fendo.2022.816599