Evaluation of Commercial Glucometer Test Strips for Potential Measurement of Glucose in Tears

Tear glucose measurements have been suggested as a potential alternative to blood glucose monitoring for diabetic patients. While previous work has reported that there is a correlation between blood and tear glucose levels in humans, this link has not been thoroughly established and additional clinical studies are needed. Herein, we evaluate the potential of using commercial blood glucose test strips to measure glucose in tears. Of several blood glucose strips evaluated, only one brand exhibits the low detection limit required for quantitating glucose in tears. Calibration of these strips in the range of 0-100 mu M glucose with an applied potential of 150 mV to the working electrode yields a sensitivity of 0.127 nA/mu M and a limit of quantitation (LOQ) of 9 mu M. The strips also exhibit <= 13% error (n = 3) for 25, 50, and 75 mu M glucose in the presence of 10 mu M acetaminophen, 100 mu M ascorbic acid, and 100 mu M uric acid. Measurements of glucose in tears from nine normal (nondiabetic) fasting human subjects using strips yielded glucose values within the range of 5-148 mu M (mean = 47 mu M, median = 43 mu M), similar to those for human tears reported by others with more complex LC-MS methods. The glucometer strip method could facilitate more clinical studies to determine whether tear glucose and blood glucose levels sufficiently correlate for application to routine measurements in tears to supplement blood glucose testing. This would be especially helpful for children, adolescents, other Type 1 diabetics, and also for Type 2 diabetics who require treatment with insulin and cannot tolerate multiple finger sticks per day.