Pathlength-independent methods for optically determining material composition

• US 20030178569A1
• Filed: 12/12/2002
• Published: 09/25/2003
• Est. Priority Date: 12/14/2001
• Status: Active Grant

• Current Assignee: OptiScan Biomedical Corporation
• Original Assignee: OptiScan Biomedical Corporation
• Inventors: Braig, James R., Sterling, Bernhard B., Hartstein, Philip C., Goldberger, Daniel S., Gaffney, Robert D.
• Granted Patent: US 7,009,180 B2
• Time in Patent Office: Days
• US Class Current: 250/339.09
• CPC Class Codes: A61B 2562/0295 Strip shaped analyte sensors for apparatus classified in A61B5/145 or A61B5/157
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427
• CPC Class Codes: G01N 21/35 using infrared light G01N21/39 takes precedence
• CPC Class Codes: G01N 27/3271 Amperometric enzyme electrodes for analytes in body fluids, e.g. glucose in blood amperometry per se G01N27/49; aspects concerning the enzyme reagent C12Q1/001

Abstract

A method uses spectroscopy to determine an analyte concentration in a sample. The method includes producing an absorbance spectrum of the sample. The method further includes shifting the absorbance spectrum to zero in a wavelength region. The method further includes subtracting a water or other substance contribution from the absorbance spectrum.

Claims

1. A method for using spectroscopy to determine an analyte concentration in a sample, the method comprising:

producing an absorbance spectrum of the sample;

shifting the absorbance spectrum to zero in a wavelength region; and

subtracting a water or other substance contribution from the absorbance spectrum.

2. The method of claim 1, wherein the wavelength region is at or near an isosbestic wavelength.

3. The method of claim 1, wherein the sample is a biological sample and the substance is a whole blood protein.

4. The method of claim 1, wherein the analyte concentration determination is insensitive to pathlength.

5. The method of claim 1, wherein subtracting the water contribution from the absorbance spectrum comprises:

providing a reference water absorbance spectrum;

scaling the reference water absorbance spectrum by multiplying the reference water absorbance by a scaling factor, wherein the scaled reference water absorbance spectrum approximately equals the absorbance spectrum at a predetermined wavelength; and

subtracting the scaled reference water absorbance spectrum from the absorbance spectrum.

6. The method of claim 1, wherein subtracting the substance contribution from the absorbance spectrum comprises:

providing a reference substance absorbance spectrum;

scaling the reference substance absorbance spectrum by multiplying the reference substance absorbance by a scaling factor, wherein the scaled reference substance absorbance spectrum approximately equals the absorbance spectrum at a predetermined wavelength; and

subtracting the scaled reference water absorbance spectrum from the absorbance spectrum.

7. The method of claim 1, comprising subtracting a residual interactive component contribution from the absorbance spectrum.

8. The method of claim 7, wherein the residual interactive component comprises components of a boundary layer between water and protein.

9. The method of claim 1, further comprising subtracting a potentially interfering substance contribution from the absorbance spectrum.

10. The method of claim 9, wherein the potentially interfering substance comprises urea.

11. The method of claim 1, further comprising subtracting a glucose contribution from the absorbance spectrum and determining a residual substance concentration in the sample.

12. The method of claim 11, wherein the residual substance comprises lactate.

13. The method of claim 11, wherein the residual substance comprises urea.

14. The method of claim 1, wherein the OD spectrum is fitted with reference glucose spectral data, thereby yielding a measurement of glucose concentration in the sample.

15. The method of claim 14, wherein the absorbance spectrum is fitted with reference glucose spectral data at at least one glucose absorbance maximum.

16. The method of claim 15, wherein the at least one glucose absorbance maximum is at approximately 9.25 μ

m.

17. The method of claim 15, wherein the at least one glucose absorbance maximum is at approximately 9.65 μ

m.

18. A method of providing pathlength insensitive measurements of blood constituents in a sample using infrared (IR) spectroscopy, the method comprising:

providing an absorbance spectrum of the sample;

shifting the absorbance spectrum to zero at an isosbestic wavelength, wherein water and a protein within the sample have approximately equivalent absorptions at the isosbestic wavelength.