Methods and systems for optical hemoglobin measurement

1. A method for measuring hemoglobin concentration in a whole blood sample, the method comprising:

mixing a whole blood sample with a reagent to form a prepared blood sample;

flowing the prepared blood sample into a reservoir of a sensor, the sensor comprising a transparent portion configured to allow an optical measurement of an absorbance or reflectance of the prepared blood sample in the reservoir of the sensor;

detecting, using an analyzer into which at least a portion of the sensor has been inserted, the prepared blood sample in the reservoir of the sensor;

upon detecting the liquid prepared blood sample in the reservoir, optically measuring an absorbance or reflectance of the prepared blood sample using a light source and a detector in the analyzer, wherein optically measuring the absorbance or reflectance of the prepared blood sample using the light source and the detector in the analyzer comprises:

emitting light with the light source in the detector such that the light passes through the transparent portion of the sensor and is reflected by a porous, reflective material within the reservoir that absorbs the prepared blood sample; and

measuring an intensity of the light reflected by the porous, reflective material using the detector; and

determining a concentration of hemoglobin in the prepared blood sample based on the measured absorbance or reflectance and a calibration curve that relates the absorbance or reflectance to the concentration of hemoglobin in the prepared blood sample.

2. The method of claim 1 , wherein the light source is configured to emit light at a specific wavelength and the calibration curve is determined based on the specific wavelength.

3. The method of claim 2 , wherein the detector is configured to measure light at the specific wavelength.

4. The method of claim 2 , wherein the specific wavelength is between 250 nm and 950 nm.

5. The method of claim 2 , wherein the specific wavelength is between 350 nm and 450 nm.

6. The method of claim 2 , wherein the specific wavelength comprises an isosbestic point of the prepared blood sample.

7. The method of claim 1 , wherein optically measuring the absorbance or reflectance of the prepared blood sample using the light source and the detector in the analyzer comprises:

emitting light with the light source in the detector such that the light passes through the transparent portion of the sensor and into the prepared blood sample in the reservoir; and

measuring an intensity of the light after the light passes through the prepared blood sample using the detector.

8. The method of claim 7 , measuring the intensity of the light after the light passes through the prepared blood sample using the detector comprises measuring the intensity of the light that is reflected from a reflective surface in the sensor.

9. The method of claim 8 , wherein the reflective surface is positioned within the reservoir on a first side of the reservoir that is opposite a second side of the reservoir that includes the transparent portion.

10. The method of claim 1 , wherein the porous, reflective material within the reservoir is positioned on an inner surface of the transparent portion of the sensor.

11. The method of claim 1 , wherein optically measuring the absorbance or reflectance of the prepared blood sample using the light source and the detector in the analyzer comprises comparing a measured an intensity of light detected by the sensor to a reference intensity.

12. The method of claim 11 , further comprising measuring the reference intensity by:

illuminating an empty sensor with the light source; and

measuring a reflectance of the empty sensor with the detector.

13. The method of claim 11 , further comprising:

measuring internally reflected stray light by detecting an intensity of light reflected from a light absorbing surface on the sensor;

subtracting the measured internally reflected stray light from the reference intensity and the measured intensity.

14. The method of claim 13 , wherein measuring the internally reflected stray light comprises measuring the internally reflected stray light by detecting the intensity of light reflected from a light absorbing surface on the sensor as the sensor is inserted into or withdrawn from an analyzer.

15. The method of claim 1 , where the reagent comprises at least a lysing agent.

16. The method of claim 1 , further comprising:

pulsing the light source at a first frequency; and

demodulating the detector at the first frequency.

17. The method of claim 16 , wherein demodulating the detector at the first frequency removes substantially any signal that does not correspond to light pulsed at the first frequency.