Response to Jungheim and Koschinsky

In a recent letter of observation, Jungheim and Koschinsky (1) reported on their findings about a risky delay of hypoglycemia detection by glucose monitoring at the arm. Given the possible significant implications of their findings, we repeated their experiment in our own clinical unit in an institutional review board (IRB)-approved study. We would hereby like to report on our results with 10 patients (4 women, 6 men, 6 type 1 diabetic, and 4 type 2 diabetic subjects; age [mean ±SD] 49 ±14 years, mean disease duration: 50 ±14 years). During an oral glucose tolerance test (OGTT) phase, results obtained from the arm with no rubbing (Soft-Sense; Abbott Medisense) were lower than the results obtained with our reference method (Super GL; Mueller Apparatebau) from the fingertip, but the differences were clinically acceptable. However, during an intravenous intervention phase, the results from the arm nicely tracked the results obtained from the fingertip. There was no potential risk for overlooking development of a hypoglycemic episode in any of the experiments, even in the two cases where we reached glucose levels <70 mg/dl (Fig. 1).

The differences between our data and the observations from Jungheim and Koschinsky may be due to differences in 1) the experimental design, e.g., how extreme and artificial the experimental conditions were; 2) the testing device; 3) the patient populations; and 4) the methodology, including how the skin was prepared and how the blood was collected.

It also has to be considered that the artificial design chosen by Jungheim and Koschinsky does not match with the daily treatment situation, and it is rather unlikely that such rapid glucose decreases occur when not induced by intravenous insulin treatment. Therefore, in another IRB-approved study using the same devices, we explored the performance of alternative site testing in a regular treatment situation with preprandial insulin treatment before a standardized test meal (66 g carbohydrate) in 10 patients with type 1 diabetes (6 women, 4 men, age 35 ±11 years, mean disease duration 13 ±13 years). In a randomized crossover setting, they either received an appropriately calculated dose of regular human insulin 20–30 min before the meal or only 25% of this dose on the other experimental day. The arm measurements were not different from the fingertip measurements in both treatment arms, even in the phase of glucose increase after an insufficient insulin dose (Fig. 2).

Because our data and those of other studies (2) suggest good performance of the Soft-Sense meter regarding accuracy and precision in daily practice, we consider this device to be a suitable alternative option for virtually pain-free glucose monitoring in daily practice. If confirmation of an alternative site test is desired, the user can always simply perform a finger test with the same device. Furthermore, more practical studies will be required to establish whether patient groups or circumstances exist where alternative site testing should not be performed.