Practice question

Latex agglutination inhibition assay for pregnancy detects human chorionic gonadotropin. Particles coated with hCG and antibodies against hCG are mixed with urine. In absence of hormone, antibody bridges latex beads coated with antigen, producing visible clumps indicating negative result. When sample contains high hCG, free hormone saturates antibody binding sites, occupying paratopes and preventing cross-linking of latex particles. Consequently suspension remains smooth and milky without clumping. This absent agglutination reflects hormone competition successfully blocking lattice formation, interpreted as positive test, distinguishing from direct agglutination kits where clumping signifies positivity.