In vivo evaluation of a chip based near infrared sensor for continuous glucose monitoring

• A semi invasive near infrared (NIR) sensor for continuous glucose monitoring integrated with microfluidic chip and microdialysis is demonstrated.
• The sensor is based on difference absorption spectroscopy in the 1st overtone band only.
• In vitro measurements showed a limit of detection of 20 mg/dL.
• In vivo tests showed a MARE value of 13.8%.

In this paper we describe the concept and in vivo results of a minimally invasive, chip-based near infrared (NIR) sensor, combined with microdialysis, for continuous glucose monitoring. The sensor principle is based on difference absorption spectroscopy in selected wavelength bands of the near infrared spectrum (1300 nm, 1450 nm, and 1550 nm) in the 1st overtone band. In vitro measurements revealed a linear relationship between glucose concentration and the integrated difference spectroscopy signal with a coefficient of determination of 99% in the concentration range of 0–400 mg/dl. The absolute error in this case is about 5 mg/dl, corresponding to a relative error of about 5% for glucose concentrations larger than 50 mg/dl and about 12% in the hypoglycemic range (<50 mg/dl). In vivo measurements on 10 patients showed that the NIR-CGM sensor data reflects the blood reference values adequately, if a proper calibration and a signal drift correction is applied. The mean MARE (mean absolute relative error) value taken over all patient data is 13.8%. The best achieved MARE value is at 4.8%, whereas the worst lies at 25.8%, leading to a standard deviation of 5.5%.