Hemoglobin test strip and analysis system

• US 20040156037A1
• Filed: 02/11/2003
• Published: 08/12/2004
• Est. Priority Date: 02/11/2003
• Status: Active Grant

• Current Assignee: Instrumentation Lab Co (Instrumentation Lab)
• Original Assignee: International Technidyne Corporation (Sphingotec GMBH)
• Inventors: Mawhirt, James A., Cimini, Catherine, Naphuket, Supinan R., Lee, Ted, Law, Wai, Toms, Charles E.
• Granted Patent: US 7,379,167 B2
• Time in Patent Office: Days
• US Class Current: 356/39
• CPC Class Codes: B01L 2200/026 Fluid interfacing between devices or objects, e.g. connectors, inlet details
• CPC Class Codes: B01L 2300/0825 Test strips
• CPC Class Codes: B01L 3/5023 with a sample being transported to, and subsequently stored in an absorbent for analysis
• CPC Class Codes: G01N 21/8483 Investigating reagent band test-element handling not specific to a test method G01N33/4875; analytical elements specific to chemical analysis of biological material G01N33/52; autometer with reagent band G01N35/04
• CPC Class Codes: G01N 33/721 Haemoglobin

Abstract

The apparatus and method for quickly measuring the hemoglobin content of a sample of blood uses a light reflectance measurement of the hemoglobin sample lysed in a membrane. The reflection is inversely proportional to hemoglobin concentration. A blood sample is loaded on to a nylon mesh and dispersed within a nylon membrane, both of which have been treated with a hemolyzing agent and surfactant, and air-dried. As soon as the blood sample contacts the reagent on the membrane, the red blood cells are lysed and the hemoglobin molecules are released and dispersed into the membrane by the action of surfactant. The hemoglobin apparatus emits light at 522 nm to the reflective surface of the membrane. The intensity of the reflected light is measured by a detector in less than 29 seconds. The intensity of the reflected light is converted to hemoglobin concentration, g/dL, or mmol/L by an interpolative comparison with stored reflection data indicative of known hemoglobin contents.

Claims

1. Apparatus for quickly measuring the hemoglobin content of a blood sample, comprising:

a porous substrate having a light reflecting surface and adapted to receive a sample of blood, a reagent impregnated into and permeating said substrate and operative to cause lysing and rapid permeation of a blood sample applied to said substrate;

a light source selectively operated to illuminate said reflecting surface of said substrate to cause a predetermined amount of light to reflect from said substrate according to the hemoglobin content of said blood sample;

a detector for intercepting said reflected light to provide a signal indicative of the magnitude of said reflected light;

an indicator responsive to said signal for providing an output indicative of said hemoglobin content.

2. The apparatus according to claim 1 wherein said porous substrate is a nylon, or similar membrane with a pore size between 0.6 to 0.8 μ

m.

3. The apparatus according to claim 1 wherein said reagent includes a hemolyzing agent and a surfactant.

4. The apparatus according to claim 3 wherein said hemolyzing agent is saponin.

5. The apparatus according to claim 4 wherein said surfactant is sodium dioctyl sulfosuccinate (AOT), or Benzalkonium Chloride (BAC).

6. The apparatus according to claim 5 wherein said reagent includes at least 1% of surfactant, at least 2% of saponin, maltodextrin, ethanol and some dye colorant and some preservative with the remainder being water or BAC.

7. The apparatus according to claim 1 wherein said light source is at a wavelength of between 500 to 550 nm.

8. The apparatus according to claim 1 wherein said sample of blood is between 10 to 60 microliters.

9. The apparatus according to claim 1 wherein said reagent is 10 to 15 microliters per substrate.

10. The apparatus according to claim 1 wherein said hemoglobin content of said blood sample can vary between 4 to 24 g/dl of said blood sample volume.

21. The methods according to claim 1 yielding rapid results in 5 to 29 seconds.

11. Apparatus for measuring the hemoglobin content of a blood sample, comprising:

a housing having an internal hollow with a front opening accessing said hollow,

a test strip having an aperture on a surface thereof, said test strip adapted to be inserted into said housing front opening a given distance to cause said test aperture strip to be positioned over said housing and accessible with said hollow, said strip having a mesh covering the sample application side of the aperture to enhance dispersion and a porous membrane covering the bottom of said aperture, said membrane having a light reflecting surface precisely located facing said hollow when said strip is inserted, said mesh, aperture and membrane impregnated with a reagent operable to cause lysing and rapid spreading of an applied blood sample,

a light source located in said housing hollow and positioned to illuminate said light reflecting surface of said membrane,

a detector located in said housing hollow for receiving reflected light from said membrane and for providing a signed indicative of the intensity of said reflected light, and

a comparator for comparing said signal with stored signals to produce an output indicative of hemoglobin content as determined by light reflected from said membrane surface.

12. The apparatus according to claim 11 wherein said membrane is nylon or similar material with a pore size of between 0.6 to 0.8 μ

m and between 0.16 to 0.18 millimeters thick.

13. The apparatus according to claim 11 where said reagent contains a hemolyzing agent and a surfactant.

14. The apparatus according to claim 13 wherein said hemolyzing agent is saponin and said surfactant is BAC or AOT.

15. A method of determining the amount of hemoglobin in a blood sample, comprising the steps of:

lysing a sample of blood into a membrane having a reflective surface and containing a reagent suitable for lysing said sample,

directing a beam of light on said reflective surface to cause an amount of light to be reflected according to the blood lysed,

intercepting said reflected beam to provide a signal indicative of the amount of said reflected light,

comparing said signal with stored calibration signals indicative of tested reflected light from known blood samples,

providing a value indicative of the hemoglobin content of said sample interpolating between closest compared values.

16. The method corresponding to claim 15, comprising the steps of first providing a reflected light signal from said membrane before lysing said aperture with said sample of blood.

17. The method according to claim 15 wherein said light has a wavelength of 522 nm.

18. The method according to claim 15 wherein said membrane is nylon having a pore size of about 0.6 to 0.8 μ

m with a thickness of about 0.15 millimeters, to accommodated 10 to 15 microliter aliquot of reagent.

19. The method according to claim 18 wherein said reagent contains a saponin hemolyzing agent and a BAC or AOT reagent.

20. The method according to claim 15 wherein said reagent contains 2.5% saponin, 2.5% maltodextrin, 1.5% AOT, 0.002% coloring, a small amount of phenol and tartrazine and the remainder being water, or, 2.5% saponin, 2.5% BAC, 0.002% coloring and the remainder water.

22. The method according to claim 15 which allows for remote application of the blood sample onto the test strip.

23. The method according to claim 15 which allows for an initial test strip blanking and test strip removal for a remote sample application.

24. The method according to claim 15 which utilizes a kinetic measurement, and further includes the steps of taking reflectance reading every 1 second and declaring an end point when the difference in two consecutive readings is under a predetermined percentage.

26. A method according to claim 24 which includes a method of determining the uniformity and adequacy of the sample coloration of the test surface utilizing a Kinetic Low Volume Threshold technique which compares the slope created by the end point readings for two consecutive readings of the Remission values of the test LED to the slope created by two comparable readings of the second LED as the criteria for test completion has been reached.

25. A method of determining the amount of hemoglobin in a blood sample, comprising the steps of:

lysing a sample of blood into a membrane having a reflective surface and containing a reagent suitable for lysing said sample,

directing a beam of light on said reflective surface to cause a reduction in the amount of light to be reflected according to the blood lysed, the hemoglobin released and the light absorption of that hemoglobin,

intercepting said reflected beam to provide a signal indicative of the amount of said reflected light,

comparing said signal with stored calibration signals indicative of tested reflected light from known blood samples, and a blank test surface without sample,

providing a value indicative of the hemoglobin content of said sample according to said closest compared stored signal, adjusted to each strip lot by the code member.