Chemistry: analytical and immunological testing – Thyroid hormone tests
Reexamination Certificate
1998-03-19
2003-04-15
Chin, Christopher L. (Department: 1641)
Chemistry: analytical and immunological testing
Thyroid hormone tests
C436S510000, C436S524000, C436S528000, C436S530000, C436S020000, C436S021000, C436S808000, C436S814000, C436S818000, C436S825000, C436S514000, C435S004000, C435S007370, C435S012000, C435S030000, C435S032000, C435S034000, C435S038000, C604S001000
Reexamination Certificate
active
06548309
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an improvement in rapid and highly sensitive assays for ligands contained, or suspected of being contained, in liquids of non-uniform character in which solid particles and/or other undissolved substances of a semisolid or colloidal nature that are likely to interfere with or obscure the result of the assay typically are also present. Such liquids include, e.g., blood, urine, lymph, lacteal fluid, and like biological liquids and liquids that have been deliberately constituted such as inoculated bacterial media, dilutions thereof, dilutions of biological samples, etc., and non-biological liquids that contain solids, semisolids or colloids as collected such as groundwater and other environmental samples, sea water, surface water, potable water, liquid from heating, ventilation and air conditioning systems, waste water and like liquids. The assay may be an immunoassay performed in a disposable solid state device comprising a suitably housed test strip which is in turn comprised of sorbent material and which defines a flow path along which the liquid test sample travels to a test site impregnated with a conjugate of (1) a binding partner for the ligand sought to be detected, and (2) a particulate material that produces visible color in the presence of the ligand. The improvements achieved by using this invention can also be beneficially realized in assays other than immunoassays, such as receptor or molecular probe assays.
A test device suitable for immunoassay may be so constituted that it performs the assay in either the sandwich or the competition mode. Such a test device is often constructed so as to yield a quantitative result for the ligand, but it may also be designed and constructed so as to furnish only a positive or negative answer concerning the presence of the ligand. Its flow path may be designed for unidirectional or bidirectional flow of components.
The assay in which the benefits of this invention are realizable must be extremely sensitive, so that it is able to detect very low concentrations of ligand in the test fluid accurately—i.e., without producing the false positive or false negative results often experienced when using both currently sold disposable solid state devices and prior art assay methods which required multiple dilutions of the biological fluid. The latter assays in the prior art often employed, e.g., “dipstick” type devices and the like and required relatively long incubation times for reaction of the ligand with its labeled binding partner. Obviously because the test fluids referred to above typically contain solid and semisolid particles and/or other undissolved components such as fats and other colloidal substances that may interfere with or obscure the result of an assay for a particular dissolved ligand, it is important to provide for removal of these potential interferants prior to the performance of the assay itself.
U.S. Pat. No. 5,714,389 issued Feb. 3, 1998 to Charlton et al. describes assays performable on bodily fluids containing solid particulate material using specially constructed test devices which are adapted to be dipped directly into the fluid. In these devices the sample flow path is constructed so as to include, near its ingress, a filtration means having the purpose to trap particulate components of the liquid test sample as that sample flows toward the test site. The patent alleges that the inclusion of this filtration means contributes to the sensitivity and accuracy of the test, and especially to the low incidence of false positives, including borderline false positives, observed from its use.
An important object of the present invention is to achieve all of the advantages of the test system disclosed in the Charlton et al. patent, including sensitivity and rapidity of the assay, low incidence of false positives and ability to yield reliable results even in the hands of untrained personnel, without experiencing the disadvantages of the specific test device therein described. In particular, an object of this invention is avoidance of the need for directly dipping the test device into the biological test fluid, coupled with avoidance of the need for interposing a filtration means in the flow path of the sample. By dispensing with such a filtration means, one avoids problems that are experienced in instances where the filter means becomes at least partially clogged, or even wholly clogged, by solid, semisolid and/or colloidal particles contained in the test fluid, making it necessary to discard the device without obtaining any useful assay result.
Another important object of this invention is to improve the reliability of delivery to an assay system that will benefit therefrom, whether of the immunoassay, molecular probe assay, receptor assay or some other assay type, of a relatively constant and reproducible sample volume to the test device.
SUMMARY OF THE INVENTION
The invention involves the use of a swab which contacts the test sample by immersion therein so that it is wetted, and preferably saturated, with the test sample liquid. The wetted swab is then removed from the sample and applied to a test device. In immunoassay applications, the sample applied to the test device is placed in contact with a test strip which has been designed and constructed to assay specifically for a particular ligand suspected of being present in the test liquid. The swab entraps solid and semisolid particulate matter and other undissolved matter such as fats and other colloidal material contained in the test sample and delivers only the liquid portion of the sample which is to be assayed into contact with the test strip. Typically, the sample then moves along a flow path, reacting with a binding partner that has been conjugated to a label. In cases where the test sample is, e.g., urine, many known test devices for home use require the user to contact the device with a urine stream. According to the present invention, the user will be instructed to contact the swab (which is supplied firmly attached to a handle) with the urine stream and then apply the swab to the sample device. Use of the swab thus eliminates all risk of device contamination with unrelated substances; it also minimizes the potential for contact of the urine by the user's hands.
Preferably the swab is formed of a loose, fluffy fibrous material but other fibrous materials and certain open-pore materials, such as foamed resins and rubbers and sponges can also be used. Closed-cell materials that lack fibrous structure, however, are unsuitable for the swabs used in this invention. Swabs have been widely used heretofore to apply medicaments, to dry exposed surface areas of an inanimate object or a mammalian body, or to collect a small specimen of material to be viewed or further treated by moving the swab across a surface—e.g., the “throat swab” referred to in Example 1 of application Ser. No. 07/706,639 now U.S. Pat. No. 6,168,956 of Howard Chandler, assigned to SmithKline Diagnostics, Inc., but exclusively licensed in a wide area of applications to Binax, Inc., the intended assignee of the present application. Swabs have also been used heretofore to collect solid or semisolid samples in small quantities—e.g., phlegm, sputum, nasal discharge, etc.—for microscopic viewing or transfer to another receptacle for further processing.
According to this invention, the swab is to be immersed in the liquid sample, whereby liquid is sorbed by it and solid, semisolid and colloidal particles either cling to it or are left behind in the liquid. In contrast, swabs have been used in the past to collect samples by moving them across a semi-dry surface (such as the back of a patient's throat) or touching them to a mass of semisolid matter. In this invention, when the swab, after immersion in the test liquid, is deposited in a partially covered swab well in accordance with this invention as hereinafter more fully described, the absorbed liquid sample is largely expelled, but the entrained solids, semisolids and colloids that cling to a
Moore Norman James
Sy Vincent Anthony
Binax, Inc.
Chin Christopher L.
Do Pensee T.
Sears Mary Helen
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