Patent ID: 7001775

Claim:
A method of detecting in a sample of body fluid the presence of at least one of first and second autoantibodies to at least one antigen, which method comprises: (a) providing a first antibody to said antigen, wherein said first antibody is immobilized at a discrete detection position on a substrate and binds a first binding site of said antigen; (b) providing a second antibody to said antigen, wherein said second antibody is labeled to allow detection of autoantibodies when present in said sample, binds a second binding site of said antigen and is non-immobilized so that said second antibody flows along said substrate according to step (e); (c) providing a source of said at least one antigen, said antigen comprising a first binding site to which either the first autoantibody or the immobilized antibody binds and a second binding site to which either the second autoantibody or the non-immobilized antibody binds; (d) contacting said antigen of step (c) with said sample of body fluid and simultaneously or successively said non-immobilized antibody, so as to obtain a mixture wherein said antigen binds with said first and/or second autoantibodies present in said sample of body fluid, and/or said non-immobilized antibody; (e) allowing said mixture obtained in step (d) to flow along said substrate of step (a) to said immobilized antibody; and (f) monitoring binding of said antigen with either said first and/or second autoantibodies, or said immobilized or non-immobilized antibodies, by detection of the absence or presence of said labeled non-immobilized antibody at said discrete detection position, so as to provide an indication of the presence of said autoantibodies in said sample of body fluid; wherein said first and/or second autoantibodies when present in said sample respectively bind with said first and second binding sites of said antigen in step (d) so that respective binding of said immobilized and/or non-immobilized antibodies with said first and second binding sites of said antigen is completely or partially inhibited; and wherein (i) in the absence of said first and second antibodies said labeled non-immobilized antibody is detectable at said discrete detection position on said substrate, or (ii) in the presence of said first and or second autoantibodies said labeled non-immobilized antibodies not detectable at said discrete detection position on said substrate, or is detectable at a reduced level compared to (i).