Chemistry: analytical and immunological testing – Involving diffusion or migration of antigen or antibody
Reexamination Certificate
2000-02-09
2002-04-02
Nguyen, Bao-Thuy L. (Department: 1641)
Chemistry: analytical and immunological testing
Involving diffusion or migration of antigen or antibody
C436S514000, C436S518000, C436S528000, C436S541000, C436S810000, C435S007100, C435S007940, C435S287100, C435S287200, C435S805000, C435S810000, C435S970000, C422S051000, C422S051000, C422S067000
Reexamination Certificate
active
06365417
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to assays, and particularly to lateral flow assays in which a liquid analyte is applied to a sample zone of a test strip, allowed to migrate along the strip by capillary action, and detected in a capture zone.
BACKGROUND OF THE INVENTION
Assays are frequently used to detect the presence of analytes in aqueous test samples in clinical and forensic medicine, and for environmental testing, food contaminant testing, and drug use testing. There is a growing demand for such assays that are based on reactions between specifically reactive substances, and that can be conducted outside of the laboratory setting, for example at home.
There are a number of over-the-counter (“OTC”) home testing and health care professional (“HCP”) diagnostic devices that can be used to collect human body fluids and perform diagnostic assays. An example of such a diagnostic device is a dipstick used for midstream urine sampling, such as found in pregnancy testing, or testing of urine from a specimen placed in a receptacle. Both OTC and HCP diagnostic devices can be lateral flow devices, in which a liquid specimen is applied to a sample zone of a lateral flow chromatographic test strip. The strip is usually made of a porous carrier material (such as nitrocellulose) so that the liquid travels along the strip by capillary action to an indicator zone, which indicates a presence, absence, or quantity of the analyte. Sometimes a wick is attached to the strip to help move the liquid specimen into or along the sample zone. Numerous lateral flow analytical devices have been disclosed, and include those shown in U.S. Pat. Nos. 4,775,636; 4,703,017; 4,861,711; 4,855,240; 4,857,453; 4,943,522; 4,945,042; 4,496,654; 5,001,049; 5,075,078; 5,126,241; 5,451,504; 5,424,193; 5,712,172; and WO92/12428; WO 94/01775; and WO 97/06439, each of which is incorporated by reference.
Many lateral flow devices are one-step lateral flow assays in which a biological fluid is placed in a sample area on a bibulous strip, and allowed to migrate along the strip until the liquid comes into contact with a specific binding partner that interacts with an analyte in the liquid. Once the analyte interacts with the binding partner, a signal (such as a fluorescent dye) indicates that the interaction has occurred. Multiple discrete binding partners can be placed on the strip (for example in parallel lines) to detect multiple analytes in the liquid. The test strips can also incorporate control indicators, which provide a signal that the test has adequately been performed, even if a positive signal indicating the presence (or absence) of an analyte is not seen on the strip.
Although lateral flow devices have been widely used in clinical practice, there are still obstacles to both clinical and home use because of the difficulty obtaining some specimens (such as blood), or the reluctance of users to collect certain specimens (such as urine). Even in situations in which urine tests are widely used (such as urine analysis for drug testing), it can be awkward or distasteful to obtain the specimens for analysis. Moreover, it is sometimes difficult to positively identify a specimen as coming from a particular individual, because of the possibility that specimens have been mislabeled or exchanged after collection but before testing.
U.S. Pat. No. 5,910,122 (D'Angelo) discloses a saliva collector which encases a tip of an aspirating pipette, for subsequent analysis in a separate test. U.S. Pat. No. 5,380,492 shows another saliva collector which incorporates an indicator in the collector that changes color when sufficient saliva has been collected. U.S. Pat. No. 4,635,488 is a body fluid sampling device which has an absorbent nib that collects saliva and conducts it to an analysis element in an interior of a tube. The analysis element can be placed in the tube after saliva collection is completed. Alternatively, liquid communication between the nib and analysis element is altered by a porous, absorbent but hydrophobic disc that conducts the saliva to the analysis element after being wetted with a wetting agent.
A problem that has retarded the more widespread use of intra-oral collection devices is that regulatory agencies and test subjects have been concerned about the reverse migration or reflux of detection reagents from the device into the mouth. Such reflux could cause a test subject to experience a noxious taste, or even carry potentially harmful detection reagents into the mouth of the subject.
Many lateral flow tests are used for regulatory or legal purposes, and proper identification of the test subject is important. Prior devices have included a label on which identifying information can be written (for example, in U.S. Pat. No. 5,380,492). However, incorrect information can be intentionally or unintentionally entered on such labels.
It would be advantageous to provide a simple and convenient assay that is suitable for home use, avoids reflux of test reagents, and/or which can readily identify a person from whom the biological specimen is obtained.
SUMMARY OF THE DISCLOSURE
The present invention is a lateral flow device for analyzing analytes in a liquid, such as drug metabolites in saliva. In some of the disclosed embodiments, the lateral flow device includes a collection member which communicates with a lateral flow member that includes test result indicators which signal the presence, absence and/or quantity of analytes in a test liquid. The collection member absorbs or adsorbs a liquid (such as saliva in the mouth) to which the collection member is exposed. A removable barrier between the collection member and the lateral flow member inhibits the flow of liquid from the collection member when the removable barrier is present, but permits the liquid to flow into and through the lateral flow member when the barrier is removed. In some embodiments, a sufficiency indicator may be displayed by the collection member to indicate when a sufficient amount of saliva has been collected to remove the barrier.
In particularly disclosed examples, the barrier may be a negative barrier or a positive barrier. A positive barrier is a substantially liquid impermeable barrier, for example a substantially liquid impermeable plastic sheet. In some embodiments, the lateral flow member overlaps the collection member or abuts it in end to end contact, and the removable barrier may be a removable spacer interposed between the collection member and the lateral flow member. Alternatively, the liquid impermeable barrier may be a negative barrier, such as a gap between the collection member and the lateral flow member. Instead of removing such a barrier, the gap is closed, for example by sliding the collection member and the lateral flow member into contact with one another. In a particularly disclosed embodiment, the collection member and lateral flow member slide into an overlapping contiguous relationship.
The present device may be used for collecting oral secretions for subsequent analysis. A particularly suitable intra-oral device includes a housing that holds the lateral flow member and at least a portion of the collection member, with the collection member extending outside of the housing for placement in the mouth. The removable barrier may be contained within and accessible from outside of the housing, to permit the removable barrier to be removed from the between the collection member and lateral flow member when sufficient oral secretions (such as saliva) have been collected. The housing may define one or more windows though which the test result indicators can be viewed on the lateral flow member. It my be advantageous to close the windows, with clear or magnifying materials such as glass or plastic, to help isolate the interior of the housing from the oral environment.
The housing may also include slots through which a portion of the barrier extends to an exterior of the housing. An interior portion of the barrier is interposed between the collection member and the lateral flow member, so that the external portion
Fleming William H.
Hyatt Timothy P.
Thomas Dudley B.
A-Fem Medical Corporation
Klarquist & Sparkman, LLP
Nguyen Bao-Thuy L.
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