Patent ID: 6183972
Filing Date: 2001-02-06
Classification: G01N,Y10S

Abstract:
A method for determining the concentration of an analyte in a fluid test medium susceptible of exhibiting a high-dose hook effect, which comprises:a) providing a strip of a test matrix through which the test fluid suspected of containing the analyte can flow by capillarity which strip has at least two distinct capture regions in which are immobilized antibodies specific to a first epitope of the analyte and labeled antibodies whose labels provide a detectable signal and which antibodies specific to a second epitope of the analyte which in or applied to the strip upstream from the capture regions and which are able to flow through the strip along with the fluid test medium upon its application to the strip;b) applying the fluid test medium to the strip and allowing it to flow along the strip carrying the labeled antibodies with it to thereby contact the immobilized antibodies in the distinct capture regions and, when sufficient analyte is present in the fluid test medium to partially block binding of the immobilized antibody with the first epitope of the analyte in at least the first distinct capture region with which the fluid comes into contact as it flows along the strip to form a sandwich of the immobilized antibody, analyte and labeled antibody in the distinct capture regions through which the fluid test medium carries analyte the quantity of which sandwich formation is limited by the partial blocking of the immobilized antibody;c) quantitatively detecting the signal from the label on the labeled antibody in each of the distinct capture regions in which the sandwich has formed to obtain a pattern of signals which pattern is unique to the concentration of analyte in the fluid test medium; andd) mathematically combining the unique pattern of signals to create a monotonous dose-response curve to factor out the blocking of the binding between the immobilized antibody and the first epitope of the analyte;e) determining the concentration of analyte by determining where the response for a given fluid test medium falls on the dose-response curve.