Minimum procedure system for the determination of analytes

• US 20030073152A1
• Filed: 06/24/2002
• Published: 04/17/2003
• Est. Priority Date: 08/13/1986
• Status: Active Grant

• Current Assignee: Franklin A. Jurik, Geoffery Mcgarraugh, Raymond D. Underwood, Roger Phillips
• Original Assignee: Franklin A. Jurik, Geoffery Mcgarraugh, Raymond D. Underwood, Roger Phillips
• Inventors: Phillips, Roger, McGarraugh, Geoffery, Jurik, Franklin A., Underwood, Raymond D.
• Granted Patent: US 6,821,483 B2
• Time in Patent Office: Days
• US Class Current: 435/14
• CPC Class Codes: C12Q 1/54 involving glucose or galactose
• CPC Class Codes: G01N 2021/4757 Geometry 0/45° or 45/0°
• 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 21/4738 Diffuse reflection precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration, e.g. also for testing fluids, fibrous materials
• 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 33/52 Use of compounds or compositions for colorimetric, spectrophotometric or fluorometric investigation, e.g. use of reagent paper and including single- and multilayer analytical elements immunological elements G01N33/54386; involving labelled immunochemicals G01N33/58; for haemoglobin or occult blood G01N33/72
• CPC Class Codes: G01N 33/521 Single-layer analytical elements
• CPC Class Codes: G01N 33/523 the element being adapted for a specific analyte
• CPC Class Codes: G01N 33/66 involving blood sugars, e.g. galactose
• CPC Class Codes: G01N 35/1016 Control of the volume dispensed or introduced
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
• CPC Class Codes: Y10S 435/805 Test papers
• CPC Class Codes: Y10S 435/808 Optical sensing apparatus
• CPC Class Codes: Y10S 435/81 Packaged device or kit
• CPC Class Codes: Y10T 436/112499 with sample on test slide
• CPC Class Codes: Y10T 436/144444 Glucose

Abstract

A method for determining the presence of an analyte in a fluid is described along with various components of an apparatus specifically designed to carry out the method. The method involves taking a reflectance reading from one surface of an inert porous matrix impregnated with a reagent that will interact with the analyte to produce a light-absorbing reaction product when the fluid being analyzed is applied to another surface and migrates through the matrix to the surface being read. Reflectance measurements are made at two separate wavelengths in order to eliminate interferences, and a timing circuit is triggered by an initial decrease in reflectance by the wetting of the surface whose reflectance is being measured by the fluid which passes through the inert matrix. Repeatability is insured by a normalization technique performed on the light source before each reading, and an alignment method operated on the reagent strip prior to emplacement on the apparatus. The method and apparatus are particularly suitable for the measurement of flucose levels in blood without requiring separation of red blood cells from serum or plasma.

Claims

1. A reagent strip for measuring glucose in a whole blood sample, said reagent strip adapted for emplacement in a reflectance reading apparatus, said reagent strip comprising:

a porous matrix;

a signal producing system embedded in said porous matrix for reaction with said whole blood sample; and

a tab attached to said porous matrix for handling of said reagent strip after emplacement of said blood sample on said porous matrix.

2. The reagent strip of claim 1 wherein said porous matrix comprises a hydrophilic membrane in which said membrane contains openings in the rage of about 0.6 microns to about 1.0 microns.

3. The reagent strip of claim 1 wherein said signal producing system comprises glucose oxidase, peroxidase and a dye indicator.

4. The reagent strip of claim 3 wherein said dye indicator is an MBTH-DMAB (3-methyl-2-benzothiazolinone hydrazone hydrochloride and 3-dimethylaminobenzoic acid) indicator.

5. The reagent strip of claim 1 wherein said porous matrix is stably maintained at a pH of less than about 4.8 and in a solution of about 10% citrate.

6. The reagent strip of claim 5 wherein said proous matrix is stably maintained at a pH of about 4.0.

19. The reagent strip of claim 1 wherein said second membrane side is ready for reading by said second smooth membrane side without separation of said blood sample into component parts.

7. A reagent strip for measuring glucose in a whole blood sample wherein said reagent strip is adapted for emplacement in a reflectance reading apparatus, said reagent strip comprising:

a porous hydrophilic membrane having pores in the range of about 0.6 microns to about 1.0 microns;

a signal producing system of glucose oxidase, peroxidase and a dye indicator embedded in said membrane for reaction with said whole blood sample; and

a tab attached to said porous matrix for handling of said reagent strip after emplacement of said blood sample on said porous matrix.

8. The reagent strip of claim 7 wherein said strip is maintained at a pH of less than about 4.8 and in a solution of about 10% citrate.

9. The reagent strip of claim 8 wherein said pH is about 4.0.

10. The regent strip of claim 7 wherein said dye indicator is an MBTH-DMAB indicator.

11. The reagent strip of claim 7 wherein said hydrophilic membrane is maintained in a polyamide solution with a positive charge and contains at least two smooth sides, the first of said sides attached to said tab, said blood sample capable of placement on said first side such that said sample migrates to the second of said sides.

12. The reagent strip of claim 7 wherein said tab comprises a rectangular plate shaving two ends, said rectangular plate containing a centralized hole for attaching said porous membrane, said rectangular plate having a notch cut out of one of said ends.

13. The reagent strip of claim 12 wherein said notch is capable of engagement with a post on said reflectance reading device to ensure repeatable alignment of said membrane above a reflectance reader.

14. The reagent strip of claim 12 wherein said hydrophilic membrane contains two smooth sides, the first of said smooth membrane sides attached to said tab at said centralized hole, said blood sample capable of insertion in said first membrane side through said hole such that said sample migrates to the second of said smooth membrane sides.

15. The reagent strip of claim 14 wherein said strip is ready for reading by said reflectance measuring apparatus upon saturation of said second smooth membrane side.

16. The reagent strip of claim 15 wherein said second smooth membrane side has an area of about 10 mm² to about 50 mm².

17. The reagent strip of claim 16 wherein said second smooth membrane side has a diameter of about 2 mm to about 10 mm.

18. The reagent strip of claim 15 wherein said second membrane side is ready for reading by said reflectance measuring apparatus upon the placement of about 5 microliters to about 10 microliters of blood sample on said hydrophilic membrane.

20. The reagent strip of claim 15 wherein said second membrane side is ready for reading upon the emplacement of a threshold volume of said blood sample on said hydrophilic membranes, said reagent strip capable of reading said blood samples regardless of the volume of said blood sample implaced on said reagent strip above said threshold volume.

21. The reagent strip of claim 20 wherein said threshold volume is about 5 microliters to about 10 microliters of said whole blood sample.

22. A reagent strip for measuring glucose in a whole blood sample, said reagent strip adapted for emplacement in a reflectance reading apparatus, said reagent strip comprising:

a tab adapted for emplacement in said reflectance reading apparatus, said tab including a thin rectangular plate having two ends on either side of a centralized hole of about 2 mm to about 10 mm diameter, one of said ends having a notch about midway along said end;

a porous hydrophilic-membrane having two smooth sides, a first of said sides attached to said tab at said centralized hole, said membrane containing pores having openings in the range of about 0.6 microns to about 1.0 microns; and

a dye solution embedded in said porous membrane including glucose oxidase, peroxidase and an MBTH-DMAB indicator, said dye solution maintained in said hydrophilic membrane at a pH of less than about 4.8 and in a 10% citrate solution,

said reagent strip capable of measuring whole blood samples without separating said sample into components, once a threshold volume of blood sample is placed within said hydrophilic membrane.

23. The reagent strip of claim 22 wherein said blood sample is capable of emplacement through said centralized hole onto said first side of said hydrophilic membrane, said blood sample further capable of migrating to said second side of said hydrophilic membrane, wherein reflectance measurement readings can be taken by said reflectance reading apparatus.

24. The reagent strip of claim 23 wherein said threshold volume is about 5 microliters to about 10 microliters of said whole blood sample.

25. A method of aligning a reagent strip having a notch on one of its ends and a centralized hole, in a reflectance reading apparatus having a post situated adjacent to an optical reading device, comprising:

abutting said notch on said reagent strip against said post on said reflectance reading device such that said notch can rotate about said post to cause said centralized whole to be placed above said optical reading device.

26. The method of claim 25 wherein said reflectance reading apparatus contains a channel in tandem with said notch, said post located within said channel, and said reagent strip further including a narrow thin rectangular plate with a width similar to that of said channel and having two ends, said notch located within a first of said ends, said method further comprising the step of placing said rectangular plate within said channel upon abutment of said notch against said post, said placement in said channel causing said optical reading device to fit below said centralized hole seated in said channel.

27. A method of aligning a reagent strip having a notch on one of its ends and a centralized hole, with a reflectance reading apparatus having on optical reading device beneath of a channel having approximately the same width as said reagent strip, said channel further containing a post at one of its ends, said method comprising placing said strip in said channel and causing said notch to abut against said post, then rotating said strip about said post such that said centralized hole becomes placed above said optical reading device, and said. reagent strip becomes seated within said channel.

28. A method of timing of a measurement in a reflectance-reading device, which comprises:

taking at least one first optical reflectance reading from a first surface of a porous matrix on a reagent strip prior to application of a sample to a second surface of said matrix;

taking at least one additional reflectance reading from said first surface; and

comparing said additional reflectance reading to said first reflectance reading and initiating time measurement upon a predetermined drop in reflectance resulting from said sample reaching said first surface.

29. The method according to claim 28 further including taking at least one measurement reflectance reading at a predetermined time after said additional reflectance reading differs from said reflectance value by said predetermined difference.

30. The method of claim 29 wherein said surface is initially dry and said additional reflectance reading differs from said first reflectance value when a liquid assay medium consisting of a dye mixed with blood penetrates to said first surface of said matrix.

31. The method of claim 30 wherein said dye precursor is a combination of glucose oxidase, peroxidase and an MBTH-DMAB dye.

32. The method of claim 30 wherein said predetermined time is at least 20 seconds.

33. The method of claim 30 wherein said predetermined time is at least 30 seconds.

34. The method of claim 30 wherein said predetermined time is at most 45 seconds.

35. In a reflectance switching system having an optical reader capable of reading the reflectance of light emitted from a plurality of light emitting diodes (LED), said light reflected to said optical reader from a porous membrane, a method of normalizing said reflectance switching system comprising:

scanning said porous membrane for an intensity reflectance reading of said LEDs prior to the emplacement of an assay sample;

inputting said reading into a control means, said control means capable of storing readings of the intensity of said LEDs, said control means further capable of equating the difference between a pair of initial and subsequent LED readings; and

using said control means to boost the power to adjust the intensity of said LEDs to give the same reflectance reading for each LED.

36. A method for determining glucose levels in blood comprising:

placing a drop of blood on a reagent strip;

placing said strip in a reflectance scanning meter wherein said meter is sensitive to the presence of said blood sample on said reagent strip, said reflectance scanning meter initiating a timing sequence upon sensing the presence of said blood sample in said reagent strip;

taking reflectance measurements;

(1) from the background within said meter (R_b);

(2) before said reagent strip contains blood (R_dry); and

(3) at a predetermined time (R_t), then computing R*t wherein

R*t=(R_t−

R_b)/(R_dry−

R_b);

using R*t to compute K/S−

t, wherein K/S−

t is defined as

(1−

R*t)²/(2×

R*t); and

computing glucose levels from said K/S−

t value.

37. The method of claim 36 wherein said predetermined time is 20 seconds and said glucose level is defined as:

−

55.75+0.1632×

(K/S−

t,−

(5.765×

10<sup>−

5</sup>)×

(K/S−

t)²+(2.58×

10<sup>−

8</sup>)×

(K/S−

t)³.

38. The method of claim 36 wherein said predetermined endpoint in time is 30 seconds and said glucose level is defined as:

−

55.25+0.1334×

(K/S−

t)−

(2.241×

10<sup>−

5</sup>)×

(K/S−

t)²+(1.20×

10<sup>−

8</sup>)×

(K/S−

t)³.

39. A method for determining glucose levels in blood comprising:

placing a drop of blood on a reagent strip;

placing said strip in a reflectance scanning meter, wherein said meter is sensitive to the presence of said blood sample on said reagent strip, said reflectance scanning meter initiating a timing sequence upon sensing the presence of said blood sample in said reagent strip;

taking reflectance measurements;

(1) from the background within said meter (R_b);

(2) before said reagent strip contains blood (R_dry);

(3) at 15 seconds after said reagent strip contains blood (R₁₅); and

(4) at a predetermined endpoint (R_t);

using said readings to compute R*15 and R*t according to the following properties;

R*15=(R₁₅−

R_b)/(R_dry−

R_b) R*t=(R_t−

R_b)/(R_dry−

R_b)

computing K/S₁₅ and K/S_t levels where said levels are defined as;

K/S₁₅=(1−

R*15)²/(2×

R*15) K/S_t=(1−

R*t)²/(2×

R*t)

normalizing said K/S₁₅ value to arrive at a K/S_15n value defined as

K/S_15n=(1.54×

K/S₁₅)−

0.1333

arriving at a K/S_t/15 value defined as

K/S_t/15=K/S_t−

K/S_15n; and

using said K/S_t/15 value to compute said glucose levels.

40. The method of claim 39 wherein said predetermined end time is 20 seconds and said glucose level is defined as:

−

0.1388+0.1064×

(K/S_t/15)+(6.259×

10<sup>−

5</sup>)×

(K/S_t/15)²−

(6.12×

10<sup>−

8</sup>) ×

(K/S_t/15)³+(3.21×

10<sup>−

11</sup>)×

(K/S_t/15)⁴

41. The method of claim 39 wherein said predetermined end time is 30 seconds and said glucose level (YSI) is defined as:

1.099+0.05235×

(K/S_t/15)+(1.229×

10<sup>−

4</sup>)×

(K/S_t/15)²−

(5.83×

10<sup>−

8</sup>)×

(K/S_t/15)³+(1.30×

10<sup>−

11</sup>)×

(K/S_t/15)⁴