Method for non-invasively determining the concentration of an analyte by compensating for the effect of tissue hydration

A method for determining the concentration of an analyte in a sample of intact tissue, said method comprising the steps of:

• (a) measuring at least one optical property of said sample of intact tissue at at least one wavelength at an initial time, said at least one wavelength being in the range of from 550 nm to 1450 nm;
• (b) calculating the absorption coefficient and the reduced scattering coefficient of said sample of intact tissue at said initial time;
• (c) repeating the measurement of said at least one optical property of said sample of intact tissue at at least a later time at said at least one wavelength;
• (d) calculating the absorption coefficient and reduced scattering coefficient of said sample of intact tissue at at least said later time;
• (e) calculating the change in the value of the absorption coefficient at said at least one wavelength to indicate the change in the water content of said sample of intact tissue and the change in the value of the reduced scattering coefficient to indicate both the change in the water content of said sample of intact tissue and the change in concentration of an analyte in said sample of intact tissue;
• (f) correcting the value of the reduced scattering coefficient to account for the effect of the change in the water content of said sample of intact tissue;
• and
• (g) calculating the concentration of said analyte by means of the corrected value of the reduced scattering coefficient, wherein said light wavelengths at which said absorption coefficient is determined correspond to wavelengths of maximum absorption of a compound that is found in the sample of intact tissue.