A test called the Treponema pallidum hemagglutination assay, or TPHA, is used to identify and measure the amount of dissolved antibodies in a patient s serum against the causes of syphilis, a sexually transmitted disease that results in papules and nodules all over the person s body. As an alternative, hereditary transmission may potentially be the cause. It uses a hemagglutination technique to identify Palladium antibodies (HAI). To get results, fowl erythrocytes are sensitised with T. palladium particles. Sensitized erythrocytes (Test Cells) group together and create a distinctive structure on the microtiter plate when anti-Palladium antibodies are present.