The TPHA (Treponema Pallidum Hemagglutination) is an indirect
hemagglutination test for the qualitative and semi-quantitative detection of
specific anti-T. pallidum antibodies in human serum. Stabilized avian
erythrocytes sensitised with an antigenic T. pallidum solution, agglutinates in the
presence of anti-T. pallidum antibodies to give a characteristic patterns.