Purpose: To describe a dermally non-invasive serial sampling technique and to test its clinical feasibility with regard to glucose measurement.
Methods: A standardized skin mini-erosion devoid of the epidermal barrier, and covered by an artificial one, was formed by a suctioning technique. Interstitial fluid (IF) was extracted serially by brief application of negative pressure, and its glucose content compared with that in capillary or venous blood samples.
Results: The procedure caused no discomfort. The epidermis regenerated rapidly after experimentation. There were no complications. In non-diabetic subjects (n = 13) the mean of all IF values measured daily for 6 days was 6.2 +/- 0.1 mmol/l (+/-SE). The corresponding capillary blood glucose value was 5.6 +/- 0.1 mmol/l, and the venous glucose value was 5.4 +/- 0.1 mmol/l. The differences between IF glucose values and invasive control values remained within narrow limits throughout. The 2SD limits of agreement for the differences were 1.44 mmol/l (IF vs. capillary blood samples) and 1.76 mmol/l (IF vs venous samples) respectively. The OGTT curves suggested glucose kinetics to be similar in IF and in capillary blood. In diabetic subjects, the mean of IF values determined serially during one day was 15.3 +/- 1.0 mmol/l (range, 6.7-21.8 mmol/l), and the corresponding mean capillary value was 12.0 +/- 0.9 mmol/l (range, 3.3-17.2 mmol/l). The ICC for all paired photometric observations was 0.948.
Conclusions: The results suggest the new sampling technique to be a feasible approach for clinical and experimental purposes. A functionally integrated sampling patch is entering the clinical testing stage.