Overview: We performed a retrospective study that analyzed outcomes from a subset (n=20) of the Do It Yourself (DIY) closed loop community. This already well-controlled, highly motivated T1D population realized further improvements in A1c and glucose time in range (TIR), and a reduction in time spent high and low during all timeframes after beginning a DIY hybrid closed loop “artificial pancreas” system.

Objective: To compare mean BG, TIR (70-180 mg/dl), and time above and below clinically meaningful thresholds before and after OpenAPS initiation.

Methods: We performed a retrospective cross-over analysis of continuous BG readings recorded during 2-week segments 4-6 weeks before and after initiation of OpenAPS (Johns Hopkins IRB00121066). Mean BG and TIR were analyzed overall, as well as by day (7am-11pm) and night (11pm-7am), and statistical significance was assessed using paired t-tests.

Results: Mean BG and TIR improved in every time category. Overall, mean BG (mg/dl) improved (135.7 to 128.3); as did mean estimated HbA1c (6.4 to 6.1%). TIR increased from 75.8 to 82.2% overall. Overnight, BG time <70 was reduced from 6.4 to 4.2%, and time <50 was reduced from 2.3 to 1.0%. Overall, BG excursions >300 were reduced from 1.7 to 0.35%.

Conclusion: Even with tight initial control, persons with T1D saw meaningful improvements in estimated A1c, TIR, and a reduction in time spent high and low, during the day and at night, after initiating OpenAPS.

D.M. Lewis: Consultant; Self; Tandem Diabetes Care, Inc.. R.S. Swain: None. T.W. Donner: Research Support; Self; Novo Nordisk Inc., Viacyte, Inc..

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