Glucose monitoring at the thenar: Evaluation of upper dermal blood glucose kinetics during rapid systemic blood glucose changes

Objective: We compared blood glucose measurements at the thenar with those at the fingertip during glucose increase and decrease that was rapid enough to induce glucose differences between the forearm and the fingertip. Methods: A rapid glucose increase was induced by oral glucose; subsequently, a rapid glucose decrease was induced by intravenous insulin in 16 insulin-treated patients with diabetes. Capillary samples were taken in parallel from the thenar and fingertip. Different glucose monitors (FreeStyle(TM), OneTouch(R)Ultra, Soft-Sense T) were used. Additional samples were taken from the forearm (n = 10 patients) in order to demonstrate that the blood glucose change achieved was rapid enough to principally induce glucose differences at alternative sites. Results: Neither blood glucose at baseline (135 +/- 34 vs. 136 +/- 41 mg/dl, p = 0.86) nor glucose amplitude during increase (190 +/- 35 vs. 188 +/- 41 mg/dl, p = 0.65) or decrease (255 +/- 32 vs. 257 +/- 45 mg/dl, p = 0.83) differed significantly between the fingertip and the thenar. Intra-individual average thenar-fingertip glucose difference was -2 +/- 12 (p = 1.00) and +5 +/- 9 mg/dl (p = 0.11). In the subgroup, intra-individual average forearm-finger difference was -50 +/- 19 (p<0.01) and +45 ± 11 mg/dl (p < 0.01) during glucose-increase and decrease, respectively. There were no obvious device-specific differences. Conclusions: Blood glucose measurements at the thenar are a safe alternative to measurements at the fingertip at steady state as well as during blood glucose change that is sufficiently rapid to induce clinically relevant differences between forearm and fingertip.