Chemistry: analytical and immunological testing – Involving an insoluble carrier for immobilizing immunochemicals
Utility Patent
1997-06-25
2001-01-02
Chin, Christopher L. (Department: 1641)
Chemistry: analytical and immunological testing
Involving an insoluble carrier for immobilizing immunochemicals
C422S051000, C422S051000, C422S051000, C422S067000, C435S007900, C435S014000, C435S028000, C435S287100, C435S287200, C435S287700, C435S287800, C435S805000, C435S810000, C435S970000, C436S514000, C436S169000, C436S170000, C436S805000, C436S810000, C436S815000
Utility Patent
active
06168957
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a dry phase test strip for measuring the concentration of an analyte in a biological fluid; more particularly, a strip that has built-in calibration.
2. Description of the Related Art
Dry phase reagent test strips incorporating enzyme-based compositions are used extensively in clinical laboratories, physicians' offices, hospitals, and homes to measure the concentration of certain analytes in biological fluids. These strips have, for example, measured glucose, cholesterol, proteins, ketones, phenylalanine, or enzymes in blood, urine, or saliva. Measuring glucose concentration in samples of whole blood is a particularly common use. In fact, reagent strips have become an everyday necessity for many of the nation's several million people with diabetes. Since diabetes can cause dangerous anomalies in blood chemistry, it can contribute to vision loss, kidney failure, and other serious medical consequences. To minimize the risk of these consequences, most people with diabetes must test themselves periodically, then adjust their glucose concentration accordingly, for instance, through diet, exercise, and/or with insulin injections. Some patients must test their blood glucose concentration as often as four times or more daily.
It is especially important for persons who must control their diet in order to regulate sugar intake and/or administer insulin injections, and who must be guided in this regard by frequent tests of blood glucose concentration, to have a rapid, inexpensive, and accurate test.
Test strips are known that contain a testing reagent that turns a different shade of color, depending on the concentration of glucose in a blood sample that has been applied to the strip. The blood glucose concentration is measured by inserting a strip into a meter that is basically a reflectance photometer, which determines the concentration from the change in color caused by the reaction between the testing reagent and blood glucose. The testing reagent typically contains an enzyme, such as glucose oxidase, which is capable of oxidizing glucose to gluconic acid lactone and hydrogen peroxide; an oxidizable dye; and a substance having peroxidative activity, which is capable of selectively catalyzing oxidation of the oxidizable dye in the presence of hydrogen peroxide. (See, for example, U.S. Pat. No. 4,935,346, issued Jun. 19, 1990, to Phillips et al.)
Whether the test is conducted in the home, physician's office, clinic or hospital, accuracy and reproducibility of the glucose determination are extremely important. However, these strips, by their nature, do not lend themselves to large-scale manufacture with adequate strip-to-strip reproducibility from one batch to the next. Consequently, it is necessary to assign to each lot of strips a calibration code that corrects for this variability. The calibration code may be marked on the strip container, and the user must enter the code into the meter when he or she begins to use a new batch of strips. If the user fails to enter a new calibration code or enters an incorrect one, the resulting value of glucose will be incorrect. Thus, it is advantageous to incorporate the calibration code on the strip, so that the meter can “read” the calibration code before calculating the glucose concentration. In that way, there is no involvement of the user, who typically is unaware that calibration is needed.
U.S. Pat. No. 4,476,149, issued on Oct. 9, 1984, to Poppe et al., discloses an analysis test strip and process for making it that includes on-strip calibration information. The strip includes a “test field” in which the analysis takes place and a batch-specific bar code, which provides calibration information specific to strips made in a particular batch. (See also U.S. Pat. Nos. 4,510,383 and 4,592,893.) In principle, the process provides a strip whose calibration is “transparent” to the user; i.e., the user is unaware of the calibration step. While that is a highly desirable result, it comes at a high price. The bar code must be printed very precisely, with tight tolerances on the width and spacing of the bars, over the entire length of the web that constitutes a single batch of (uncut) strips. Moreover, the printing must be done in a way that does not change the characteristics of the test field. Furthermore, the meter must have a sophisticated optical system in order to read the tightly-spaced bar code reliably (See U.S. Pat. No. 4,510,383).
U.S. Pat. No. 5,281,395, issued on Jan. 25, 1994, to Markart et al., discusses the practical problems raised by the strip of Poppe, et al. and addresses some of them with a two-strip system. The “test carrier” contains the reagent for reacting with the analyte to be measured and the “code carrier” has the calibration bar code that is characteristic of a particular batch. Each carrier also has a machine-readable batch identification. This approach reduces the technical difficulties and expense involved in manufacturing the strips of Poppe et al; however, it requires the use of a second strip in order to calibrate the meter.
U.S. Pat. No. 3,907,503, issued on Sep. 23, 1995, to Betts et al., discloses a test system for measuring a variety of analytes, using a single strip. The strip includes a code means that identifies the particular test device and one or more reagents for the particular tests done by that strip. The code means does not provide a calibration for any of the reagent systems. In its simplest form, it is an opaque area attached to a generally transparent carrier. The nature of the test device is identified by the position of the code means relative to the reagent test areas. The code means may also include a distinctive mark or color, which can be recognized by the meter as identifying a particular type of strip.
Connolly, in PCT Application W096/13707, published on May 9, 1996, discloses an apparatus and method for detecting various analytes in body fluids, using dry test strips. In one embodiment, test strips are color coded to identify the test that a particular strip is intended for. Thus, a blue strip may measure glucose and a red strip cholesterol. The colors are divided into shades, for example 64 shades of blue represent 64 different lot numbers of glucose strips. The apparatus has a memory module which stores a lot number. If the lot number measured from the strip doesn't match the lot number in the memory module, the test isn't performed. This approach requires that each batch of test strips have a memory module, which is inserted into the apparatus before the strips of that batch can be used.
U.S. Pat. No. 5,515,170, issued on May 7, 1996, to Matzinger et al., discloses a reagent strip for measuring the concentration of glucose in whole blood. The strip has a testing pad that contains a reagent system that changes color to indicate the glucose concentration. The testing pad is formed from an anisotropic membrane, which has relatively large pores near one major surface and smaller pores near the opposite surface. A porous transport medium is attached to the large-pore surface of the pad. The whole blood sample is applied to the transport medium, which transfers a detectable portion of the sample to the large-pore side of the pad. Glucose in the sample then moves toward the opposite side, where it reacts with the reagent to cause a color change that is visible from the small-pore side of the pad and that indicates the glucose concentration in the sample.
There is a need for a reliable system that incorporates calibration code information on a strip in a way that does not make excessive demands on the strip-manufacturing process, yet eliminates the need for a user to be involved in calibration.
SUMMARY OF THE INVENTION
In accordance with the present invention a diagnostic test strip for measuring an analyte concentration in a sample of biological fluid, comprises
(a) a membrane, having a sample side, to which the fluid sample is applied, and a testing side, opposite the sample side;
(b) a tes
Harding Ian
Matzinger David
O'Neil Michael
Chin Christopher L.
Lifescan Inc.
Riesenfeld James
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