Tools for Rapid Diagnosis of Syphilis

Two groups of antibodies formed after infection with syphilis can be quickly detected by new tests.

The causative organism of syphilis is Treponema pallidum, a spirochete that cannot be grown on culture media or in tissue culture. The infection is normally diagnosed by the detection of antibody specific for T pallidum in the patient's blood or cerebrospinal fluid (CSF). Detection of the antibody becomes possible three to four weeks following infection.

The first group of antibodies, called regain antibodies, is formed in response to infection. These can be detected by using a rapid agglutination test that is simple to perform and takes less than 10 minutes. This is the VDRL Carbon Antigen Test (DR525M) from Oxoid (Basingstoke, UK; www.oxoid.com).

The second group of antibodies is reactive with the specific antigens of T pallidum. These antibodies persist long after the infection has been successfully treated and can be detected by a sensitive, passive hemagglutination test, the TPHA test from Oxoid. When diluted positive samples are mixed with the test cell suspension in a microtiter plate, antibody to the sensitizing antigen causes agglutination of the cells. The cells form a characteristic pattern on the bottom of the plate well.

Oxoid notes that syphilis rates in the UK have increased by 500% in the past six years, up by 67% in males and 33% in females.




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