Treponema Palladium Haemagglutination Test (TPHA Test)

The Treponema Pallidum Haemagglutination Assay (TPHA Test) is a blood test used to detect antibodies against the bacteria Treponema pallidum, which causes syphilis. This test is typically used as a confirmatory test after a positive screening test for syphilis, such as the Rapid Plasma Reagin (RPR) test or Venereal Disease Research Laboratory (VDRL) test.

During the TPHA test, a small amount of the patient's blood is mixed with a suspension of red blood cells that have been coated with a T. pallidum antigen. If the patient has antibodies against T. pallidum, these antibodies will bind to the antigen-coated red blood cells and cause them to clump together, or agglutinate. The degree of agglutination can then be measured to determine the presence and level of antibodies against T. pallidum.

The TPHA test is a highly specific and sensitive test for syphilis, but it is not able to differentiate between current or past infection. It is often used in conjunction with other tests to help diagnose and monitor the treatment of syphilis.

What is the purpose of the TPHA test for syphilis?

The TPHA test detects antibodies against Treponema pallidum bacteria to help confirm syphilis infection. It is used after a positive initial screening test like RPR or VDRL.

How does the TPHA test work?

During the TPHA test, the patient's blood is mixed with RBCs coated with T. pallidum antigens. If syphilis antibodies are present, they cause the RBCs to clump or agglutinate.

What are the limitations of the TPHA test?

While the TPHA test is highly specific for syphilis, it cannot differentiate between a current or past infection. It may need to be interpreted along with other tests like RPR to determine disease status.