This observational study evaluated real-world glycaemic and self-reported outcomes among users of the Tandem Diabetes Care t:slim X2 insulin pump with the new Control-IQ algorithm, which uses continuous glucose monitoring (CGM) values to predict blood glucose levels 30 minutes in advance and adjust insulin delivery accordingly. This hybrid closed-loop system was approved in the US in early 2020 and is the first system approved to provide automated insulin correction boluses based on predicted CGM data.
A total of 9085 people who had newly initiated the system or upgraded their old software to incorporate the Control-IQ algorithm were invited to participate. Of these, 3116 consented to participate and 1435 completed the study. Participants uploaded their CGM data and filled in psychosocial questionnaires at two time points: at least 3 weeks after device initiation (mean, 43 days), and then 4 weeks after that, in order to determine the immediate and sustained effects of Control-IQ use.
Between the two follow-ups, median Time In Range (TIR) increased by a small but significant amount, and was 79.2% at the second assessment. Time below 3.9 and 3.0 mmol/L remained stable at 1.2% and 0.2%, respectively, while time above 10.0 mmol/L reduced to 19.0%.
A subgroup of participants (n=1127) had 30 days of CGM data available prior to and after Control-IQ initiation. Median TIR increased from 69.8% to 79.4% following the switch.
User-reported outcomes showed high device satisfaction and reduced diabetes burden throughout, with small but significant improvements between the two follow-ups. Factors contributing to user satisfaction included sensor accuracy, improved glycaemic control, reduction in extreme glucose levels, improved sleep quality and efficient connectivity to the CGM system. There was a small but significant reduction in overall wellbeing scores, which was assumed to be related to COVID-19 and the lockdowns that occurred in the US over the study period.
The study was limited by a lack of a control group and the significant risk of selection bias, given that early adopters of a new technology are likely to be most invested in its use, and given the low rates of study acceptance and completion. Nonetheless, the improvement in TIR from prior therapy, which is consistent with that seen in clinical trials, is impressive.
Pinsker JE, Müller L, Constantin A et al (2020) Real-world patient reported outcomes and glycemic results with initiation of Control-IQ technology. Diabetes Technol Ther 26 Aug [epub ahead of print]. https://doi.org/10.1089/dia.2020.0388