Chemistry: analytical and immunological testing – Composition for standardization – calibration – simulation,... – Inorganic standards or controls
Reexamination Certificate
2000-03-21
2002-09-17
Alexander, Lyle A. (Department: 1743)
Chemistry: analytical and immunological testing
Composition for standardization, calibration, simulation,...
Inorganic standards or controls
C436S008000, C436S111000, C436S163000, C436S164000, C422S067000
Reexamination Certificate
active
06451607
ABSTRACT:
BACKGROUND OF THE INVENTION
A variety of diagnostic tests for diseases and other biological conditions which utilize test products featuring built-in, specimen-activated control elements have been described in the patent literature. The purpose, utility and function of these control elements are described in U.S. Pat. Nos. 5,268,146, 5,416,003, 5,585,273, 5,571,684, and 5,660,790. All patents cited in this specification are incorporated herein by reference.
One example of a test product of this type is a self-contained test device designed to detect elevated pH and amines in vaginal fluid specimens (U.S. Pat. No. 5,660,790). The device features built-in, specimen-activated controls with an iconic readout of results. The readout is illustrated by a plus/minus sign, the positive test result being represented by a blue plus sign on a yellow background while the negative test result is represented by a blue minus sign on a yellow background. In this format, the horizontal bar generating the blue color (a yellow-to-blue color change) serves as the positive control while the non-color-changing yellow background serves as the negative control.
Another example is a self-contained test device for detection of proline iminopeptidase (PIP) activity in vaginal fluid, as disclosed in U.S. Pat. Nos. 5,268,146 and 5,571,684, again with built-in, specimen-activated controls. This device consists of a three-dimensional chamber which includes a test zone and positive and negative control zones. A positive test result is indicated by color formation (or change) in the test zone; a negative test result is indicated by the absence of color formation (or change) in the test zone. The positive control should form a color upon addition of a specimen, indicating that the indicator is indeed functioning, whereas the negative control zone should produce no such color, indicating that the device does not produce false positive results.
Products based on reporter enzyme release as described in U.S. Pat. Nos. 5,416,003 and 5,585,273 also feature built-in, specimen-activated positive and negative controls that serve purposes analogous to those of the built-in, specimen-activated positive and negative controls of the test devices of the preceding paragraphs.
The built-in, specimen-activated controls in these devices provide the user with assurance that each individual test device is in proper functioning condition. Because they are built into each device, these controls require no additional steps on the part of the user, and because they are activated by the specimen that is being tested, they can be true controls, ideally suited for this primary purpose.
Nonetheless, at least four additional factors suggest that additional value can be gained by providing dried controls, positive or negative, that are physically distinct from the test devices (i.e., separate devices) and that function independently of the built-in, specimen-activated controls:
(1) Appropriately formulated external controls can allow new users of the test device to see the appearance of a positive test result or a negative test result, prior to using the test device itself with clinical or other specimens, and thereby knowing what to expect or to look for in an actual test;
(2) Appropriately designed controls that are distinct from the test device and do not require specimen activation can provide a training opportunity for new users;
(3) The external controls can be included in a package of test devices, and the user can use the controls upon receipt of the entire package to ascertain that the materials in the test devices have not deteriorated during shipment; and
(4) Physically distinct controls that do not require specimens for activation can permit more widespread use of the test device because they may facilitate regulatory approval for use by relatively untrained personnel.
To meet these objectives, the controls must not only function properly, but they must also be inexpensive and simple to use, and they must have a shelf life at least equal to, and storage requirements no greater than, those of the test device itself. Ideally, for a control device to serve as a training aid, the color produced by the control device should be stable over an extended period of time to permit observation and discussion among trainees. Most currently available external controls usually do not meet these requirements. For example, many current external controls consist of small bottles of positive and negative liquid control reagents that are expensive to manufacture, package, ship and store. Furthermore, such reagents often require refrigeration during storage. To apply liquid external controls to test kits, the user is often instructed to bring the refrigerated control solutions to room temperature before use, and to return them to refrigerated storage immediately after use. These requirements add to the complexity of test procedure. Because of these shortcomings, liquid controls are poorly suited to use with consumer products where instructive assistance is particularly important.
SUMMARY OF THE INVENTION
The present invention resides in a control device that is designed for use with any analytical test device, and particularly a solid-phase analytical test device, that is used for analysis of a liquid sample to detect the presence of an analyte in the sample by a detectable change in an indicator in the analytical test device. The control device is distinct from the analytical test device in that no sample is applied to the control device, no chemical reaction occurs in the control device, and no detection is made or test performed in the control device. Instead, the control device merely serves as a source of control reagent(s) to be used in the analytical test device. The control reagent(s) is a dry lamina(e) on the surface of the control device which itself is entirely solid and dry, and the reagent(s) can be removed by a wet swab or other implement and then transferred by the implement to the analytical test device. Once applied to the test device, the control reagent, if it is a positive control, causes a response identical to or analogous to that which would be caused by a sample that contains the analyte, and if the control reagent is a negative control, it causes a response identical or analogous to that which would be caused by a sample that does not contain the analyte. Use of the control device in this manner allows the user to determine whether or not the analytical test device is functioning properly, ie., whether an actual sample in which the analyte of interest is present would itself produce a positive reading on the analytical test device, or whether a sample that did not contain the analyte would produce a negative reading.
The control device of this invention is described herein by the terms “physically distinct” or “functionally distinct” relative to the analytical test device. These terms are intended to mean that the control device is not functionally joined to the analytical test device, i.e., the mere application of a liquid or a sample to one does not necessarily result in the application of the liquid or sample to the other. The two devices may be on a common base or substrate, and may or may not be separable from each other by cutting the substrate or breaking it along a scored line. Preferably, the two devices are on two distinct substrates that are not connected. In this separated arrangement, the control device is characterized in parts of this specification as “external” relative to the analytical test device. The control test reagents that are contained in the control device are likewise termed “external” to distinguish them from built-in specimen-activated control reagents or zones that are part of the analytical test device itself. The control test reagents are also referred to as “positive” and “negative” control reagents. The term “positive” in this context refers to a reagent which, when applied to the analytical test device, produces the same indicator response that would be produced if a sample containing the
Andreasen Terrence J.
Lawrence Paul J.
Pena Robert
Alexander Lyle A.
Litmus Concepts Inc.
Townsend and Townsend / and Crew LLP
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