Patent ID: 7501287

Claim:
An assay method for the determination of transcobalamin saturation in a transcobalamin containing liquid sample as a ratio of holo transcobalamin to total transcobalamin content, said method comprising: (i) contacting said sample with a porous substrate having immobilized thereon a transcobalamin-immobilizing antibody, whereby to generate immobilized transcobalamin; (ii) before, during or after step (i) above, contacting transcobalamin of said sample with a first reporter-labelled binding antibody for transcobalamin, said first binding antibody binding both holo and apo transcobalamin or being a specific binding antibody for apo transcobalamin, and with a second reporter-labeled binding antibody for holo transcobalamin which has a specificity for holo transcobalamin vs apo transcobalamin of at least 10-fold whereby to immobilize said first and second reporter-labeled binding antibodies by their binding to the immobilized transcobalamin, said first and second reporter labeled antibodies producing interdistinguishable signals; and (iii) detecting signals from the reporter labels of said first and second reporter-labeled binding antibodies immobilized on said substrate, and determining therefrom a holo transcobalamin level and a total transcobalamin level in said sample and calculating the transcobalamin saturation in said sample as the ratio of the holo transcobalamin level to the total transcobalamin level.