Which Threshold to Detect Hypoglycemia?

Value of receiver-operator curve analysis to find a compromise between sensitivity and specificity

The Diabetes Control and Complications Trial (DCCT) showed that the improvement of glycemic control by intensive insulin therapy resulted in a decrease in the risk of late diabetic complications. However, this effect was associated with an increase (by a factor of 3) in the risk of severe hypoglycemia (1). This explains the interest in the development of a hypoglycemic alarm that uses continuous glucose monitoring. Several approaches to this are possible.

Noninvasive methods have the benefit of measuring glucose without breaking the cutaneous barrier. Generally, these methods are based on the principle of the analysis of the absorption of the light in a zone of the spectrum close to the infrared, or of the diffraction of the light in the skin. These two parameters are indeed influenced by the level of glycemia, but sensitivity and specificity of these methods are far from providing sufficiently useful miniaturized systems that can be used in clinical practice (2). In invasive methods, the system of measurement (or a part of the system of measurement) is placed inside the body. The system can be totally implantable, requiring that both the sensor and the electronic control system are miniaturized, which is currently possible. In addition, the system must work for a time period sufficiently long to avoid the need for frequent implantations. The sensitive part of the system (the sensor) may be placed directly into a blood vessel (3) or in subcutaneous tissue (4). Nevertheless, for obvious reasons, most of the invasive systems that have been developed so far use transcutaneous access.

Two basic approaches have been attempted. In the first approach, the glucose sensor has the shape of a needle that is implanted under the skin and is …