Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Calorimeter
Reexamination Certificate
1999-11-15
2004-02-10
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Calorimeter
C422S105000, C422S105000
Reexamination Certificate
active
06689317
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatus for the diagnosis of allergies. In particular, the invention relates to immunoassay apparatus that does not require sophisticated laboratory equipment or technical expertise and is suitable for use in the home or the doctor's surgery.
A number of kits using immunoassay technology (mainly for pregnancy testing or fertility prediction) are widely available for use in the home or in a doctor's surgery. The format of the immunoassay technique in such kits is broadly similar, utilizing test strips containing immobilized immunoreactant and requiring the user to provide and apply a sample of a predetermined body fluid. Some devices that use urine as the source of the analyte require no further intervention than the application of the sample to the device. This is an ideal situation where urine not only contains the analyte but also acts as the fluid component of a mobile phase which initiates the chemical reaction within the device.
However, other samples may not be readily available in such copious volumes. For applications where urine is not appropriate, a blood sample is usually required, although other body fluids may also be of use, for example, saliva or tears. Due to practical and ethical reasons, devices that are designed for use in the home and that require a blood sample must work with a capillary sample not usually larger than a few hundred microliters in volume.
For most devices, because of physical constraints such as flow properties, this volume is insufficient to initiate the chemical reaction and permit it to proceed. Additional fluid components must then be added to the kit in order to provide a mobile phase. This mobile phase can be contained within a compartment inside the apparatus, the release of which is initiated either by physical intervention by the user, or by a chemical interaction of the sample with a physical barrier separating the mobile phase from the immunoreactants. The mobile phase could also be added from a separate container to a receptacle on the device itself. Of course the more steps that are involved with the operation of the kit, the more chance there is for error by the user and less is the likelihood of obtaining a correct result.
For some medical conditions, it is important to obtain a rapid test result. For example, a result within minutes of sample application may be required with a test to be used in emergency situations, whereas for other conditions a result within minutes may not be necessary.
Currently available apparatus is often non-sequential in nature, meaning that the reaction involves a single step. However, one of the main problems with non-sequential immunometric test kits is the occurrence of a phenomenon called a “high dose hook effect”. The high dose hook effect is evident when high levels of antigen in the system saturate the assay. This is caused by free analyte being left in the sample after reaction of all the available labelled immunoreactant and the inadequate binding capacity of the immunoadsorbent for the amount of complexed and free analyte in the system. This unlabelled analyte can then compete downstream for the immobilised immunoreactant. In some cases, when there is a large amount of analyte in the sample, false negative results can be obtained merely because of saturation of the labelled immunoreactant and immunoadsorbent. These false negative, or abnormally low, results may influence decisions on treatment made by the user or clinician. This will not occur if sufficient immunoadsorbent is present. However, there are limitations to the binding capacity of an immunoadsorbent, and it is not generally practical to increase the amount of labelled immunoreactant in the system to overcome the high dose hook effect, as this will tend to increase the non-specific binding of the labelled immunoreactant, thereby reducing the analytical sensitivity of the assay, giving rise to an elevated reference (blank) reading. In conventional laboratory immunoassays, this problem is overcome by carrying out a sequential assay, with discrete wash steps between each addition of sample and immunoreactant. Sequential immunometric assays can be easily run in a laboratory. For example, a sample which contains analyte may be allowed to react with an immobilized immunoreactant specific for the analyte in question. After a predetermined incubation period, unbound analyte in the sample may be washed away, usually by a combination of decantation and washing. Then the labelled immunoreactants are added.
A further method to circumvent the high dose hook effect, and to avoid the sequential format, would be to use a competitive assay format. However, this is not ideal. For example, with such assays, the precision is highly dependent on the region of the dose response curve being examined. In contrast to immunometric assays, the response in competitive assays is inversely proportional to the dose—that is, a lower signal is obtained with higher concentrations of analyte. In general, this is not a preferred attribute for a home testing kit where the absence of a signal confers a positive result. A preferred way to avoid the high dose hook effect while maintaining an acceptable assay format is a sequential immunometric assay approach. However, the requirement for separate addition of reagents by the user and intervening discrete wash steps, would make such a testing device too cumbersome for home or office use.
EP 0314499 A discloses a test device for carrying out an immunoassay and making a color change result visible to the user. The device comprises a first “fast” flow path and a second “slow” flow path of porous or fibrous liquid conductive material. The ends of both tracks are contacted with a sample liquid store (mobile phase containing the analyte). The first path for flow of the analyte contains an enzyme and the second path contains a labelling substrate corresponding to the enzyme. Both paths lead to a detection means.
EP 0186799 A discloses an analytical device comprising a zone for receiving sample containing an analyte, a zone for receiving the mobile phase and a detection zone. The document teaches the possibility of having two parallel flow paths which start from the mobile phase reservoir and lead the detection zone, wherein the main path transports the sample containing the analyte and the second path entrains reagents for color detection.
EP 0590695 A discloses a liquid transfer device for use in assay procedures, comprising a sheet of porous material for capillary liquid flow therethrough. The sheet is formed to define two liquid flow channels leading from two channel ends to a site in a common channel portion, where the two channels merge. The two channels are operable to deliver liquid to said common site in a sequentially timed manner following simultaneous application of such liquid to the channel ends.
OBJECTS OF THE INVENTION
The present invention aims to overcome the problems associated with non-sequential immunometric assays by providing a selfdiagnosis apparatus which can use a sequential immunoassay method, but which does not require sophisticated laboratory equipment or technical expertise.
It is an object of the present invention to provide a self diagnosis apparatus utilising immunoassay technology which is particularly useful for the measurement of antigen-specific human immunoglobulin E (IgE), as in allergy diagnosis, but which may also be used for other analytes and isotypes.
SUMMARY OF THE INVENTION
Immunoassay analytical test apparatus for allergy diagnosis according to the present invention comprises:
(a) a zone for receiving a sample containing an analyte;
(b) a zone for receiving a mobile phase, which zone may be the same as the sample receiving zone, or different thereto;
(c) a detection means for permitting detection of said analyte by immunoreaction;
(d) a first flow path for flow of said analyte in said mobile phase from said sample receiving zone to said detection means; and
(e) a second flow path permitting flow of said mobil
Clinical Diagnostic Chemicals Limited
Cross LaToya
Gordon & Jacobson P.C.
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