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 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 surface of a single-layer, substantially reflective, porous, hydrophilic membrane having pores of a size sufficient to exclude red blood cells and which contains said signal-producing system;
making said reflectance measurement on a second surface of said membrane other than the surface to which said sample is applied without removing excess sample or red blood cells from said first surface; and
determining the concentration of glucose in said sample from said reflectance measurement.
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Accused Products
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
18 Claims
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1. In 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:
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applying an unmeasured whole blood sample to a first surface of a single-layer, substantially reflective, porous, hydrophilic membrane having pores of a size sufficient to exclude red blood cells and which contains said signal-producing system; making said reflectance measurement on a second surface of said membrane other than the surface to which said sample is applied without removing excess sample or red blood cells from said first surface; and determining the concentration of glucose in said sample from said reflectance measurement. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for determining glucose comprising the sequential steps of:
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(a) applying a whole blood sample to an application site on a reagent element wherein said reagent element comprises a single-layer, substantially reflective, porous, hydrophilic matrix which filters out red blood cells and to which is bound a signal-producing system comprising glucose oxidase, peroxidase and a dye indicator, which signal-producing system reacts with glucose to form a reaction dye product; (b) allowing the sample to migrate to a reading site on said membrane different from said application site; (c) monitoring reflectance at said reading site for a decrease in reflectance indicative of sample presence in said reading site in order to initiate timing of an incubation period; and (d) determining the change in reflectance at said reading site during the incubation period as a measure of dye product formed to determine the amount of glucose in said sample wherein all reflectance measurements at said reading site are performed without removing excess sample or red blood cells from said application site and at least one measurement is taken at a wavelength at which light is absorbed by said dye product. - View Dependent Claims (11, 12, 13, 14)
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15. A method of determining analyte concentration in a liquid, which comprises:
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quantitatively measuring baseline reflectance from a first surface of a reagent element comprising an inert, porous, hydrophilic, substantially reflective, single-layer matrix having pores of a size sufficient to exclude red blood cells and a reagent system which interacts 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; applying said liquid to a second surface of said reagent element and allowing said liquid to migrate from said second surface to said first surface; quantitatively measuring reaction reflectance from said first surface of said reagent element without removing excess sample or non-migrating components of said sample from said second surface; quantitatively measuring reflectance of interfering substances from said first surface of said reagent element using a wavelength of light reflected by interfering substances and different from the wavelength of light used to measure said reaction product reflectance in order to correct for background reflectance at the reaction product wavelength caused by interfering substances; and calculating a value expressing said analyte concentration from said reflectance measurements. - View Dependent Claims (16, 17, 18)
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Specification