Reporting Insulin Pump Accuracy: Trumpet Curves According to IEC 60601-2-24 and Beyond

Accuracy of insulin pump basal rate delivery, if tested according to the standard IEC 60601-2-24 for infusion pumps, shall be presented as a trumpet curve. This way of graphical presentation is common; however, it is often misunderstood and misinterpreted by people. It is often assumed that a trumpet curve shows the error rate as a function of time, thus implying an increasing accuracy in the course of time. On the contrary, the horizontal axis of a trumpet curve shows increasingly long observation windows. In addition, trumpet curves display only extreme values, that is, those windows with minimal and maximal deviation, which might not be representative for the total deviation. This commentary provides information regarding the calculations and the interpretation of trumpet curves and proposes alternative approaches.