Hemoglobin test strip and analysis system

• US 7,379,167 B2
• Filed: 02/11/2003
• Issued: 05/27/2008
• Est. Priority Date: 02/11/2003
• Status: Expired due to Term

• Current Assignee: Instrumentation Lab Co (Instrumentation Lab)
• Original Assignee: International Technidyne Corporation (Sphingotec GMBH)
• Inventors: Cimini, Catherine, Naphuket, Supinan R., Lee, Ted, Law, Wai, Toms, Charles E., Mawhirt, James A.
• Primary Examiner(s): Toatley, Jr.; Gregory J.
• Assistant Examiner(s): Punnoose; Roy M.
• Application Number:
  US10/364,256
• Publication Number:
  US 20040156037A1
• Time in Patent Office: 1,932 Days
• Field of Search: 356/39, 356/40, 356/244, 356/246
• 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. An apparatus for quickly measuring the hemoglobin content of a blood sample, the apparatus comprising:

a test strip;

a mesh supported by said test strip, said mesh impregnated with a lysing reagent, wherein said blood sample applied to said mesh disperses across said mesh and reacts with said lysing reagent impregnated in said mesh;

a porous substrate supported by said test strip, said porous substrate impregnated with said lysing reagent and having a light reflecting surface;

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 comprises a nylon material 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.

11. Apparatus for measuring the hemoglobin content of a blood sample, the apparatus 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 a sample application side of the aperture and a porous membrane covering a bottom of said aperture, said membrane having a light reflecting surface facing said hollow when said strip is inserted, said mesh and membrane impregnated with a lysing reagent, wherein a blood sample applied to said mesh disperses across said mesh and reacts with said lysing reagent impregnated in said mesh;

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 signal 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 comprises a nylon 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, the method comprising the steps of:

lysing a sample of blood with a test strip comprising a mesh and a membrane having a reflective surface, said mesh and membrane impregnated with a lysing reagent, said lysing performed by applying said blood sample to said mesh, wherein said blood sample applied to said mesh disperses across said mesh and reacts with said lysing reagent impregnated in said mesh;

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 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.

21. The method according to claim 15, wherein the amount of hemoglobin in the blood sample is determined in 5 to 29 seconds.

22. A method of determining the amount of hemoglobin in a blood sample, the method 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;

performing a kinetic measurement including 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.

23. The method according to claim 22, further including determining uniformity and adequacy of a sample coloration of the reflective surface utilizing a Kinetic Low Volume Threshold technique which compares a slope created by end point readings for two consecutive readings of Remission values of a test LED to a slope created by two comparable readings of a second LED as criteria that test completion has been reached.

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

lysing a sample of blood with a test strip comprising a mesh and a membrane having a reflective surface, said mesh and membrane impregnated with a lysing reagent, said lysing performed by applying said blood sample to said mesh, wherein said blood sample applied to said mesh disperses across said mesh and reacts with said lysing reagent impregnated in said mesh;

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.

25. A test strip for use with an apparatus that measures a hemoglobin content of a blood sample, the test strip comprising:

a supporting strip;

a mesh disposed on the supporting strip, the mesh impregnated with a lysing reagent; and

a membrane disposed on the supporting strip adjacent to the mesh, the membrane impregnated with the lysing reagent and having a light reflecting surface,

wherein the blood sample applied to the mesh disperses across the mesh and reacts with the lysing reagent impregnated in the mesh.

26. The test strip according to claim 25, wherein the reagent includes sodium dioctyl sulfosuccinate (AOT), or Benzalkonium Chloride (BAC).