Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 25-year-old woman with type 1 diabetes presents to clinic requesting more information about use of a closed-loop insulin-delivery system (artificial beta cell).

Although her HbA1c is at goal, she notes frequent hypoglycemia as an issue. In addition, she would like to further improve her glycemic control in anticipation of pregnancy in the next few years. Her father also has type 1 diabetes managed on insulin pump therapy. Her only medication is insulin lispro administered through a sensor-augmented insulin pump therapy.

On physical examination, vital signs are normal. BMI is 21. All other physical examination findings are normal.

Laboratory studies show an HbA1c value of 6.9%.

Based on a recent study in the New England Journal of Medicine, which of the following outcomes could this patient anticipate if she transitioned to a closed-loop insulin delivery system as compared with her current sensor-augmented pump therapy?

A. Greater glucose variability
B. Increased hypoglycemia
C. Significantly higher overnight mean glucose level
D. Significantly lower mean glucose level

MKSAP Answer and Critique

The correct answer is D. Significantly lower mean glucose level.

This patient could expect a significantly lower mean glucose level with the closed-loop insulin system (artificial beta cell). The Home Use of an Artificial Beta Cell in Type 1 Diabetes study showed the feasibility, safety, and efficacy of a 12-week day-and-night application of closed-loop insulin delivery in adults under free-living conditions.

Among adults, the mean glucose level was significantly lower with day-and-night use of the closed-loop system than with sensor-augmented pump therapy, which was the control (P <0.001).

Glucose variability, measured both as the standard deviation of the sensor glucose level and as the coefficient of variation of the sensor glucose level between days, was significantly lower with day-and-night use of the closed-loop system than with the sensor-augmented pump.

The relative burden of hypoglycemia, as measured by the area under the curve when the sensor glucose level was less than 63 mg/dL (3.5 mmol/L), was significantly lower by 39% (95% CI, 24 to 51) during the intervention period than during the control period (P <0.001).

Overnight end points were similar to those during the 24-hour period. The overnight mean glucose level was significantly lower with the closed-loop system than with the control system (P <0.001), and the proportion of time that the glucose level was within the overnight target range was greater with the closed-loop system (P <0.001).

Key Point

• A closed-loop insulin delivery system (artificial beta cell) improved glucose control, reduced hypoglycemia, and resulted in a lower HbA1c level as compared with sensor-augmented pump therapy in adults with type 1 diabetes mellitus.

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