The present invention provides a method of measuring the concentration of a compound and a value of oxygen saturation in the blood of a part of a subject. Also provided is a device for carrying out the disclosed method. The method relates to measuring the concentration of a compound and a value of oxygen saturation in the blood part of a subject, and correlating the measured concentration of the compound and/or the value of oxygen saturation in the blood to a specific clinical condition. The device comprises a polychromatic light source, a receptor, a detector, and a processing system comprising a calibration algorithm.
