Assay reagents and devices

Abstract

A reagent useful in immunoassays, comprising a direct particulate level co-sensitised with a specific binding agent having specificity for an analyte or analyte analogue and with a non-specific protein which can participate in a control reaction with another specific binding agent which does not bind to the first specific binding agent nor participate in the formation of a complex by means of which detection of the analyte or analyte analogue is accomplished. Preferably the first specific binding agent is an antibody raised in a first species and the non-specific protein is an immunoglobulin from another species. Optionally, the reagent additionally comprises a second population of the direct particulate label sensitised solely with the non-specific protein.

1 . A reagent useful in immunoassays, comprising a direct particulate label co-sensitised with 
 (i) a specific binding agent having specificity for an analyte or analyte analogue, and    (ii) a non-specific protein which can participate in a control reaction with another specific binding agent which does not bind to said first specific binding agent nor participate in the formation of a complex by means of which detection of said analyte or analyte analogue is accomplished.    
   
   
       2 . A reagent according to  claim 1 , wherein said first specific binding agent is an antibody raised in a first species and said non-specific protein is an immunoglobulin from another species.  
   
   
       3 . A reagent according to  claim 2 , wherein said first specific binding agent is a murine antibody.  
   
   
       4 . A reagent according to  claim 2 , wherein said non-specific protein is a rabbit immunoglobulin.  
   
   
       5 . A reagent according to  claim 1 , additionally comprising a second population of said direct particulate label sensitised solely with said non-specific protein.  
   
   
       6 . A reagent according to  claim 2 , comprising coloured latex particles of diameter less than 0.5 micron, co-sensitised with an anti-hCG murine monoclonal antibody and with rabbit IgG.  
   
   
       7 . A reagent according to  claim 6 , additionally comprising same-coloured latex particles of diameter less than 0.5 micron sensitised solely with rabbit IgG, the ratio of said co-sensitised particles to said second particles being at least 2:1.  
   
   
       8 . An assay device according to  claim 7 , wherein said ratio is about 3:1.  
   
   
       9 . An assay device of the type wherein a sample liquid reconstitutes a labelled reagent and carries it into a detection zone and a control zone, binding of said labelled reagent in these zones revealing the assay result, wherein said labelled reagent is as claimed in  claim 1 .  
   
   
       10 . An assay device according to  claim 9 , wherein said detection zone contains an immobilised specific binding agent which acts as a direct or indirect capture means for said analyte or analyte analogue but which does not bind to said non-specific protein, and said control zone contains a specific binding agent which binds said non-specific protein but does not bind said specific binding agent co-sensitised on said first particle.  
   
   
       11 . An assay device according to  claim 9 , wherein said detection zone contains an immobilised specific binding agent which acts as a direct or indirect capture means for hCG, said control zone contains an immobilised anti-rabbit IgG antibody, and said labelled reagent is coloured latex particles of diameter less than 0.5 micron, co-sensitised with an anti-hCG murine monoclonal antibody and with rabbit IgG.