Automatic initiation of a time interval for measuring glucose concentration in a sample of whole blood

• US 5,843,692 A
• Filed: 09/30/1997
• Issued: 12/01/1998
• Est. Priority Date: 08/13/1986
• Status: Expired due to Term

• Current Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Phillips, Roger, McGarraugh, Geoffery, Jurik, Franklin A., Underwood, Raymond D.
• Primary Examiner(s): GITOMER, RALPH J
• Application Number:
  US08/941,868
• Time in Patent Office: 427 Days
• Field of Search: 435/14, 435/25, 435/28, 435/805, 435/808, 435/968, 435/970, 422/56, 422/57, 422/58
• 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 measuring a glucose concentration in whole blood uses a reagent test strip having a matrix pad and a reflectance meter. The test strip is placed in the meter, and a blood sample is applied to the top surface of the pad. As the sample travels through the pad, glucose in the blood reacts with reagent in the pad to cause a change in reflectance of its bottom surface. An incubation period is initiated when the meter detects that at least a portion of the sample has reached the bottom surface. At the end of the incubation period, the reflectance of the bottom surface is measured and used to calculate the glucose concentration.

Claims

1. A method for measuring a glucose concentration in a sample of whole blood using a reflectance-reading device, which comprises the steps of:

(a) providing a test strip for placement in the reflectance reading device, the test strip having a matrix pad with a sample receiving surface and a testing surface opposite the sample-receiving surface, which matrix pad further comprises a reagent for reacting with the glucose in the blood sample and creating a change in reflectance at the testing surface indicative of the glucose concentration in the sample;

(b) applying a sample of whole blood to the sample-receiving surface and allowing at least a portion of the sample to travel to the testing surface and react with the reagent;

(c) initiating a predetermined incubation period upon a change in reflectance at the testing surface sufficient to indicate that at least a portion of the sample has reached the testing surface;

(d) taking a reflectance measurement at the end of the predetermined incubation period, without having determined the time at which the sample was initially applied to the matrix pad; and

(e) determining the glucose concentration in the sample from the reflectance measurement.

2. A method according to claim 1, in which the reflectance-reading device includes a photo detector and the method further comprises the step of measuring a background current from the photo detector prior to step (a).

3. A method according to claim 1, further comprising the step of taking a reflectance measurement prior to step (b).

5. A method according to claim 1, wherein the incubation period is initiated upon a drop in reflectance of between 5 and 50%.

6. A method according to claim 5, wherein the incubation period is initiated upon a drop in reflectance of about 10%.

7. A method according to claim 1, wherein all steps are accomplished without removing any sample from the sample-receiving surface.

8. A method according to claim 1, wherein the reagent comprises glucose oxidase, peroxidase, and a dye precursor.

9. A method according to claim 8 wherein the dye precursor is at least one dye couple selected from the group consisting of 3-methyl-2-benzothiazolinone hydrazone hydrochloride and 3-dimethylaminobenzoic acid and 4-aminoantipyrene and chromotropic acid.

4. A method according to claim , further comprising the step of, prior to step (c), taking reflectance readings at closely spaced intervals, to determine any change in reflectance at the testing surface.

10. An apparatus for measuring a concentration of glucose in a sample of whole blood, which comprises

a) a chamber for removably accepting a test strip that includes a porous matrix pad which

(i) has a first major surface for accepting the sample and a reflective second major surface opposite to the first surface,

(ii) allows the sample to travel through the pad from the first surface toward the second surface, and

(iii) is impregnated with a reagent that reacts with glucose to cause a change in the reflectance of the second surface;

b) means for accessing the pad in the chamber to permit the sample to be applied to the first surface of the pad at an application time;

c) means for illuminating the second surface of the pad in the chamber;

d) means for monitoring intensity of light reflected from the second surface of the pad in the chamber;

e) means for initiating a predetermined time interval upon measuring a change in intensity of reflected light that is indicative of the arrival of a portion of the sample at the second surface; and

f) means for calculating the glucose concentration from the intensity of reflected light measured at the end of the time interval, without having determined the application time.

11. A method according to claim 42 wherein the matrix pad comprises polyamide.