Patent ID: 7432046
Filing Date: 2008-10-07
Classification: G01N

Abstract:
1. A method of distinguishing between acute and chronic infection in a human patient by determining the avidity of human anti-infectious agent IgG antibody in a sample from said patient, said patient suspected of having been infected by an infectious agent, comprising the steps of: a) adding at least one purified antigen from said infectious agent to a liquid phase solution to create a liquid phase antigen solution, coating said at least one purified antigen onto a solid phase to create a solid phase antigen, and removing said liquid phase antigen solution from said solid phase antigen; b) in a first assay, contacting a test sample from said patient with said liquid phase solution comprising no liquid phase antigen, c) subsequently contacting said diluted test sample, in the absence of said liquid phase antigen, with said coated solid phase of step a) for a time and under conditions sufficient for formation of antibody/antigen complexes; d) washing said coated solid phase of step c); e) in a second assay, contacting a test sample from said patient with liquid phase antigen solution, f) subsequently contacting said test sample/liquid phase antigen solution with said coated solid phase of step a) for a time and under conditions sufficient for formation of antibody/antigen complexes; g) washing said contacted solid phase antigen of step f); h) adding a conjugate to said first and second assays for a time and under conditions sufficient for formation of anti-IgG/antibody/antigen complexes in said first and second assays, wherein said conjugate comprises an anti-IgG antibody attached to a signal-generating compound capable of generating a detectable signal; i) detecting a signal generated by said signal-generating compound in said first and second assays; j) determining the ratio between said signal obtained in said second assay and said signal obtained in said first assay, wherein said ratio is proportional to the level of human anti-infectious agent low avidity IgG antibody present in said patient sample; k) multiplying said ratio of step h) by 100 and subtracting said multiplied ratio from 100 in order to determine an Avidity index, an Avidity index below a first numerical value indicating said patient has low avidity anti-infectious agent IgG and an acute infection and an Avidity index above a second numerical value indicating said patient has high avidity anti-infectious IgG and a chronic infection with said infectious agent.