Noninvasive blood glucose measurement using multiple laser diodes

Abstract

, Zhang XQ, Chen JH, Soh PH, Ng K, Yeo JH Abstract In the event of diabetes clinicians have advocated that frequent monitoring of a diabetic’s blood glucose level is the key to avoid future complications (kidney failure, blindness, amputations, premature death, etc.,) associated with the disease. While the test-strip glucose meters available in current consumer markets allow for frequent monitoring, a more convenient technique that is accurate, painless and sample-free is preferable in a diabetic’s daily routine. This paper presents a non-invasive blood glucose measurement technique using diffuse reflectance near infrared (NIR) signals. This technique uses a set of laser diodes, each operating at fixed wavelengths in the first overtone region. The NIR signals from the laser diodes are channe led to the measurement site viz., the nail-bed by means of op tical fibers. A series of in vivo experiments have been performed on eight normal human subjects using a standard Oral Glucose Tolerance Test (OGTT) protocol. The reflected NIR signals are inputs to a Partial Leas t Squares (PLS) algorithm fo r calibration and future predictions. The calibration models used are developed using in vivo datasets and are unique to a particular individual. The 1218 paired points collected from the eight test subjects plotted on the Clarke Error Grid, revealed that 87.3% of these poi nts fall within the A zone while the remainder, within the B zone, both of which, are clinically accepted. The standard error of prediction was s 13.14mg/dL for the best calibration model. A Bland-Altman analysis of the 1218 paired points yields a 76.3% confidence level for a measurement accuracy of s 20mg/dL. These results demonstrate the initial potential of the technique for non-invasive blood glucose measurements in vivo . Keywords: non-invasive blood glucose measurement, laser diodes, near infrared (NIR), diabetes, diffuse reflectance