Quantitative analyte assay device and method
The present invention related to a quantitative assay device and a method for the determination of an analyte, based on a test strip, which contains a porous test membrane allowing for capillary flow of the analyte and complexes of the analyte, a porous upstream membrane in fluid connection with the test membrane and a porous downstream membrane in fluid connection with the test membrane, wherein the test membrane contains two bands having deposited on there high and low concentrations of different calibrator agents and a test band capable of reacting with conjugated analyte complexes giving rise to a measurable signal.
1. An assay device for the quantitative determination of an analyte, comprising a test strip containing a porous test membrane allowing for capillary flow of the analyte and complexes of the analyte, a porous upstream membrane in fluid connection with the test membrane and a porous downstream membrane in fluid connection with the test membrane,
(a) said test membrane comprising (i) a test band site having immobilized thereon a ligand capable of competing with the analyte for binding a label conjugate capable of reacting with the analyte to the test band site, and, (ii) a first standard band site having immobilized thereon a first calibrator agent corresponding to a first known high concentration of the analyte, and a second standard band site having immobilized thereon a second calibrator agent corresponding to a second known low concentration of the analyte, wherein the two calibrator agents are different and are capable of reacting with different label conjugates and binding such to the standard band sites to provide a known label response in the standard band sites,
(b) said upstream membrane having a site for the application of a sample to be analyzed, and having a site downstream from the sample application site for depositing the label conjugate capable of reacting with the analyte and depositing the two label conjugates capable of reacting with the immobilized calibrator agents in the standard bands, and
(c) said downstream membrane capable of absorbing said sample and providing the capillary flow for the sample through the upstream and test membrane.
2. The device of claim 1 , wherein the label conjugates give rise to a color.
3. The device of claim 2 , wherein the label conjugates comprise gold conjugates, fluorescent dye conjugates, latex conjugates and enzyme conjugates.
4. The device of claim 1 , wherein the calibrator agents are rabbit IgG and bovine thyroid globulin.
5. The device of claim 1 , wherein the test strip is contained in a cassette allowing for the addition of the sample at the upstream membrane and for viewing the results of color formation at the sites of the test membrane.
6. The device of claim 1 , wherein the label conjugates for the analyte and for the calibrator agents are different.
7. The device of claim 1 , wherein the test membrane is microporous nitrocellulose and the upstream membrane is fiberglass.
8. The device of claim 1 , wherein the test membrane further comprises a third standard band.
9. The device of claim 1 , wherein the label conjugates generate visual signals at the test band site and standard band sites.
10. The device of claim 9 , wherein the visual signals are generated by a colloidal gold conjugate, a fluorescent dye conjugate, or a latex particle.
11. The method of claim 1 , wherein the analyte is a cardiac marker.
12. The device of claim 1 , wherein the analyte is T4, the test band site is immobilized with T4-bovine serum albumin conjugate.