Chemistry: analytical and immunological testing – Involving an insoluble carrier for immobilizing immunochemicals
Reexamination Certificate
2000-03-14
2003-04-22
Le, Long V. (Department: 1641)
Chemistry: analytical and immunological testing
Involving an insoluble carrier for immobilizing immunochemicals
C435S007100, C435S007900, C435S287100, C435S287200, C435S287700, C435S286500, C435S810000, C435S910000, C436S528000, C436S530000, C436S541000, C422S068100, C422S070000, C422S090000
Reexamination Certificate
active
06551842
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to test devices and methods for the determination of analytes which may be present in liquids.
BACKGROUND OF THE INVENTION
The quantification of chemical and biological components in aqueous sample solutions, such as whole blood, plasma, serum and urine, is important for the timely and correct diagnosis of various diseases, as well as for monitoring the progress of the medical treatment of diseases. In many cases the analytes being measured are present in only tiny amounts and are often mixed with much larger amounts of irrelevant or interfering components. Some components, such as red blood cells, prevent the analysis of the sample if they are present. Also problematic are the reagents and indicators used to detect and measure the analytes, which are often highly colored and closely resemble the reaction products in terms of their absorbance spectra. In addition, the measurement of analytes often requires multiple, incompatible reagents that must be stored separately and added sequentially. Any of these factors may complicate the detection and quantification of analytes in fluid samples.
These problems and issues have been addressed in a variety of ways. Analytical methods employed in clinical chemistry testing and other applications used can be divided into two broad categories of assay formats: liquid chemistry formats and dry chemistry formats. Liquid chemistry systems require that sample and liquid reagents be dispensed into reaction chambers in a timed, sequential order. Samples must often be diluted with special buffers to reduce or eliminate interfering compounds and are then added to reagents designed to react with specific analytes. In some cases, multiple reagents must be premixed immediately before use due to stability problems. In other cases additional reagents may be needed to provide color-producing, readable reactions. The results may be obtained by measuring the absorption of light by the fluid sample. Reactions involving decreases in reaction color or minor differences in color changes may further require separate tubes of reagents to standardize the results or serve as controls.
Dry chemistry systems utilize reagents dried onto absorbent surfaces. Most commercially available products have multiple layers of reactants sandwiched together. Some are arranged vertically and some combine vertical and horizontal arrangements. In all cases, dry chemistry systems using chromogenic reactions rely on measuring light reflected off of either the top or bottom surface of the final reagent pad. The assaying of whole blood presents additional problems since it requires a separate method for separating red blood cells from the sample such as centrifugation or the use of blood separating filter(s) which separate the plasma for analysis. The essence of dry chemistry analysis is to contain a liquid reaction so that colored reaction products can be visualized. This is done with gels and polymers, e.g., Vitros (Johnson & Johnson) or fibrous paper-like materials, e.g., Seralyzer (Bayer Diagnostics). In all cases the reaction must be observed among a mixture of sample, diluent, reactants and product which can result in difficulties distinguishing product from non-product. In addition, since all or part of the original reactant is consumed, it can be impossible to reference back to the starting material, such as to establish a reagent baseline. In contrast, the present invention retains all components for further evaluations.
In methods that require precise reaction timing, such as those requiring rapid reactions or measuring a rate of change, it is often difficult to determine the exact start time of the reactions. In most cases the performance of the assay, and therefore the reliability of the results, is dependent on the ability of the test system to evenly deliver a certain amount of liquid (usually blood plasma or serum) to a final reactant material. This material must absorb a known quantity of liquid with extreme accuracy and reproducibility in order for the results to be useful. The precise volume measurements required to obtain accurate results with these types of assays present particular challenges and make them difficult to work with.
Both liquid and dry chemistry systems are limited in the concentrations of reactants that can be used. These concentration limits are often due to the presence of highly colored reactants that absorb or reflect light at wavelengths that interfere with or obscure the detection of reaction product which may absorb or reflect light at similar wavelengths. Various methods have been employed in attempts to solve this problem. Hochstrasser, U.S. Pat. No. 3,964,871, describe a disposable indicator for measuring substances which registers the concentration of a substance in a given biological fluid with indicia which are directly readable in a convenient notation thereby reducing reliance on comparison with a color intensity scale. Kim et al., U.S. Pat. No. 4,303,408, describe elements with interferent-reducing zones which remove interferents prior to the reaction zone. Despite these attempts, only marginal improvements are possible due to the physical limitations which are inherent in the methods.
U.S. Pat. No. 5,716,852, issued to Yager et al., teaches a channel-cell system for detecting the presence and/or measuring the presence of analyte particles in a sample stream comprising a laminar flow channel, two inlets in fluid connection with the laminar flow channel for respectively conducting into the laminar flow channel an indicator stream which may comprise an indicator substance which indicates the presence of said analyte particles by a detectable change in property when contacted with said analyte particles, and the sample stream. The laminar flow channel has a depth sufficiently small to allow laminar flow of streams and a length sufficient to allow particles of the analyte to diffuse into the indicator stream to the substantial exclusion of the larger particles in the sample stream to form a detection area. An outlet conducts the streams out of the laminar flow channel to form a single mixed stream. Yager discloses the formation of a reaction interface that forms between two fluids moving through a capillary tube in the same direction. We disclose the invention of a stable interface that forms when two liquids meet and stop in a flow matrix after conveying from opposite directions. The Yager patent is predicated on the principle of liquid laminar flow, which was known in the art. In contrast, the present invention employs bibulous material to physically contain the liquid interface.
U.S. Pat. No. 5,187,100, issued to Matzinger et al., discusses a control solution for use with a porous reagent strip, and comprises a flexible semisolid polymer dispersed in water, such as polyvinyl acetate in distilled water, with appropriate control glucose concentration levels. This solution is useful in mimicking whole blood in conjunction with porous reagent strips to determine compliance of the strips and meters to established measurement and performance criteria.
U.S. Pat. No. 5,147,606, issued to Charlton et al., teaches a diagnostic device that detects blood analytes with a sample volume as low as 2 microliters in the hematocrit range of 0% to 60%, or higher. This is accomplished by employing a housing with various chambers and compartments for processing the blood. A sample application port in the housing is used to introduce blood into a metering chamber. From the metering chamber, the blood flows to a reaction chamber for analyzing blood analytes. Blood entering the metering chamber flows into a fluid capillary which indicates that an adequate amount of blood has been received in the metering chamber. The reaction compartment includes a reagent and a filter, the latter of which is disposed between the metering chamber and the reagent so that the reagent reacts with the filtered blood.
U.S. Pat. No. 4,839,297, issued to Freitag et al., teaches a test apparatus for the analytical determination of
Do Pensee T.
Foley & Lardner
IDEXX Laboratories, Inc.
Le Long V.
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