Transcutaneous glucose measurement using near-infrared spectroscopy duringhypoglycemia

OBJECTIVE - To analyze a transcutaneous near-infrared spectroscopy system a s a technique for in vivo noninvasive blood glucose monitoring during eugly cemia and hypoglycemia. RESEARCH DESIGN AND METHODS - Tell nondiabetic subjects and two patients wi th type 1 diabetes were examined in a total of 27 studies. In each study, t he subject's plasma glucose was lowered to a hypoglycemic level (similar to 55 mg/dl) followed by recovery to a glycemic level of similar to 115 mg/dl using an intravenous infusion of insulin and 20% dextrose. Plasma glucose levels were determined at 5-min intervals by standard glucose oxidase metho d and simultaneously by a near-infrared spectroscopic system. The plasma gl ucose measured by the standard method was used to create a calibration mode l that could predict glucose levels from the near-infrared spectral data. T he two data sets were correlated during the decline and recovery in plasma glucose, within 10 mg/dl plasma glucose ranges, and were examined using the Clarke Error Grid Analysis. RESULTS - Two sets of 1,704 plasma glucose determinations were examined. Th e near-infrared predictions during the fall and recovery in plasma glucose were highly correlated (r = 0.96 and 0.95, respectively). When analyzed dur ing 10 mg/dl plasma glucose segments, the mean absolute difference between the near-infrared spectroscopy method and the chemometric reference ranged from 3.3 to 4.4 mg/dl in the nondiabetic subjects and from 2.6 to 3.8 mg/dl in the patients with type 1 diabetes. Using the Error Grid Analysis, 97.7% of all the near-infrared predictions were assigned to the A-zone. CONCLUSIONS - Our findings suggest that the near-infrared spectroscopy meth od can accurately predict plasma glucose levels during euglycemia and hypog lycemia in humans.