Minimum procedure system for the determination of analytes
First Claim
1. In a method for determining glucose in a blood sample, employing a membrane and a signal-producing system that produces a light-absorptive dye product, said system being bound to the membrane, 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 whole blood to a surface of said membrane, and making said measurement on a surface of said membrance other than the surface to which said sample is applied.
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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. 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.
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Citations
27 Claims
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1. In a method for determining glucose in a blood sample, employing a membrane and a signal-producing system that produces a light-absorptive dye product, said system being bound to the membrane, 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 whole blood to a surface of said membrane, and making said measurement on a surface of said membrance other than the surface to which said sample is applied. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for determining glucose comprising the steps of:
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applying a whole blood sample to a reagent element, wherein said reagent element comprises a hydrophilic matrix to which is bound glucose oxidase, peroxidase, and a dye indicator capable of forming a reaction product;
allowing the sample to penetrate said membrane;
initiating timing of a predetermined timed reflectance readings by detecting penetration of the sample through said membrane; and
by a decrease in reflectance; and
determining the amount of glucose in said a sample by the additional change in reflectance resulting from absorbance by said dye product. - View Dependent Claims (8, 9, 10)
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11. A method of initiating timing of a measurement in a reflectance-reading device, which comprises:
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taking at least one first reflectance reading from a first surface of a porous matrix prior to application of a sample to a second surface of said matrix;
taking at least one additional reflectance reading from said first surface;
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; and
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. - View Dependent Claims (12, 13)
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14. A measuring apparatus for the determination of an analyte in a fluid, which comprises:
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a container having light-tight closure adapted to removably contain a porous matrix capable of containing an absorbed fluid to be analyzed;
means for illuminating surface of said matrix;
means for detecting light of two different wavelengths reflected from said matrix;
control means for collecting readings of reflected light and calculating a value for the amount of analyte in said fluid based on readings of analyte or reaction product absorbance from the first wavelength of reflected light and of background absorbance from the second wavelength of reflected light; and
means for reporting said value. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method of determining analyte concentration in a liquid, which comprises:
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quantitatively measuring base reflectance from a first surface of a reagent element comprising an inert porous matrix and a reagent system capable of interacting with said analyte to produce a light-absorbing reaction product, said reagent system being impregnated in the pores of said matrix, prior to application of said liquid to said reagent element;
quantitatively measuring reaction reflectance from said reagent element after application of said liquid to a second surface of said reagent element other than the first surface from which said reaction reflectance measured and after said liquid has migrated through said reagent element from said second surface to said first surface;
quantitatively measuring interference reflectance from said first surface of said reagent element after said application of liquid using a wavelength of light different from the wavelength of light used to measure said reaction reflectance; and
calculating a value expressing said concentration from said reflectance measurements. - View Dependent Claims (25, 26, 27)
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Specification