Method for detecting the presence of a residue analyte in a sample

A method for the detection of an analyte in a liquid sample comprises employing a labelled receptor that reacts with the analyte to form an analyte-receptor complex, positioning the labelled receptor within or proximate to a membrane, exposing said membrane to the liquid sample whereby lateral capillary flow occurs thereon, the liquid thereby carrying the analyte-receptor complex and any unbound labelled receptor towards a test zone positioned on the membrane in the flow path, said test zone having a representative analyte conjugate attached to the membrane to bind unbound receptor to form a first analyte conjugate receptor complex that as a result of the label has a signal visible to the eye or readable with an instrument where the receptor may bind a family of analytes which have similar structural binding sites and the method includes the step of employing additional analyte binders that bind a portion of the analyte in competition with the receptor thereby decreasing test sensitivity.