Minimum procedure system for the determination of analytes

• US 5,179,005 A
• Filed: 04/28/1988
• Issued: 01/12/1993
• 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): Moskowitz, Margaret
• Assistant Examiner(s): Fleisher, Mindy B.
• Application Number:
  US07/187,602
• Time in Patent Office: 1,720 Days
• Field of Search: 435/4, 435/14, 435/25, 435/28, 435/805, 435/808, 435/810, 436/24, 436/46, 436/63, 436/95, 436/166, 436/169, 422/56, 422/57, 422/58, 422/61, 422/68
• 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 glucose levels in blood without requiring separation of red blood cells from serum or plasma.

Claims

1. A method for determining glucose in a blood sample employing a membrane and a signal-producing system which reacts with glucose to produce a light-absorptive dye product, said system being bound to the membrane, and in which the amount of said dye product is determined by means of a reflectance measurement from a surface of said membrane, an improvement which comprises:

applying an unmeasured whole blood sample to a first porous, hydrophilic membrane having pores of a size sufficient to exclude red blood cells and which contains said signal-producing system;

placing said matrix in a reflectance scanning meter wherein said meter detects the presence of said blood sample on said matrix, said reflectance scanning meter initiating a timing sequence upon detecting the presence of said blood sample in matrix;

taking reflectance measurements;

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

(2) before said matrix contains blood (R_dry); and

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

space="preserve" listing-type="equation">R*t=(R.sub.t -R.sub.b)/(R.sub.dry -R.sub.b);

using R*t to compute K/S-t, wherein K/S-t is defined as

space="preserve" listing-type="equation">(1-R*t).sup.2 /(2×

R*t); and

computing glucose levels from said K/S-t value.

2. The method of claim 1 wherein said predetermined time is 20 seconds and said glucose level is defined as:

space="preserve" listing-type="equation">-55.75+0.1632×

(K/S-t)-(5.765×

10.sup.-5)×

(K/S-t).sup.2 +(2.58×

10.sup.-8)×

(K/S-t).sup.3.

3. The method of claim 1 wherein said predetermined endpoint in time is 30 seconds and said glucose level is defined as:

space="preserve" listing-type="equation">-55.25+0.1334×

(K/S-t)-(2.241×

10.sup.-5)×

(K/S-t).sup.2 +(1.20×

10.sup.-8)×

(K/S-t).sup.3.

4. A method for determining glucose in a blood sample employing a membrane and a signal-producing system which reacts with glucose to produce a light-absorptive dye product, said system being bound to the membrane, and in which the amount of said dye product is determined by means of a reflectance measurement from a surface of said membrane, an improvement which comprises:

applying an unmeasured whole blood sample to a first porous, hydrophilic membrane having pores of a size sufficient to exclude red blood cells and which contains said signal-producing system;

placing said matrix in a reflectance scanning meter, wherein said meter detects the presence of said blood sample on said matrix, said reflectance scanning meter initiating a timing sequence upon detecting the presence of said blood sample in said matrix;

taking reflectance measurements;

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

(2) before said matrix contains blood (R_dry);

(3) at 15 seconds after said matrix 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;

space="preserve" listing-type="equation">R*15=(R.sub.15 -R.sub.b)/(R.sub.dry -R.sub.b)

space="preserve" listing-type="equation">R*t=(R.sub.t -R.sub.b)/(R.sub.dry -R.sub.b);

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

space="preserve" listing-type="equation">K/S.sub.15 =(1-R*15).sup.2 /(2×

R*15)

space="preserve" listing-type="equation">K/S.sub.t =(1-R*t).sup.2 /(2×

R*t);

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

space="preserve" listing-type="equation">K/S.sub.15n =(1.54×

K/S.sub.15)-0.1333;

arriving at a K/S_t/15 value defined as

space="preserve" listing-type="equation">K/S.sub.t/15 =K/S.sub.t -/S.sub.15n ; and

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

5. The method of claim 4 wherein said predetermined end point is 20 seconds and said glucose level is defined as:

##EQU1##

6. The method of claim 4 wherein said predetermined end point is 30 seconds and said glucose level is defined as:

##EQU2##