Test device and method for colored particle immunoassay

A method of detecting a ligand in a liquid sample suspected of containing said ligand, the method comprising the steps of:

• (a) providing a test strip, disposed within a housing, comprising sorbent material and defining
• a flow path,
• a sample inlet, and, spaced apart from said inlet in said flow path,
• a test site having immobilized thereon a first protein having a binding site specific for a first epitope on said ligand, and
• a separate control site;
• (b) providing a conjugate comprising a metal sol particle coupled to a second protein having a binding site specific for a second epitope on said ligand;
• (c) applying to said inlet said liquid sample;
• and
• (d) transporting to said test site and said control site by sorption, capillary action, wicking or wetting along said flow path said liquid sample in admixture with said conjugate,
• thereby to produce,
• at said control site, color indicative of a valid test result and indicative that conjugate has bound specifically or non-specifically at said control site, and
• at said test site, if said ligand is present in said liquid sample, a specific binding reaction product comprising said ligand and an aggregate of said metal sol particle to produce a color visible to the unaided eye indicative of the presence of said ligand.

A method of detecting a ligand in a liquid sample suspected of containing said ligand, the method comprising the steps of:

• (a) providing a test strip, disposed within a housing, comprising sorbent material and defining
• a flow path,
• a sample inlet, and, spaced apart from said inlet in said flow path,
• a test site having immobilized thereon a first protein having a binding site specific for a first epitope on said ligand,
• a separate control site, and disposed in said flow path upstream of said test site,
• a dried reagent consisting essentional of a conjugate comprising colored particulate material coupled to a second protein having a binding site specific for a second epitope on said ligand;
• (b) applying to said inlet said liquid sample;
• and
• (c) transporting by sorption, capillary action, wicking or wetting along said flow path said liquid sample into contact with said dried conjugate to produce an admixture of said liquid sample and said conjugate, and thereafter transporting said admixture into contact with said test site and said control site thereby to produce,
• at said control site, color indicative of a valid test result and indicative that conjugate has bound specifically or non-specifically at said control site, and
• at said test site, if said ligand is present in said liquid sample, a specific binding reaction product comprising said ligand and an aggregate of said colored particulate material to produce a color visible to the unaided eye indicative of the presence of said ligand.