CAMLPR Microbiology Practice Test

Screening for syphilis uses a non-treponemal test because it is inexpensive, widely available, and sensitive to active infection. These tests detect antibodies to cardiolipin-lecithin-cholesterol antigens, which rise during the first stages of syphilis and often decline with successful treatment, allowing not only detection but also monitoring of disease activity through measurable titers. Because the result can be influenced by other conditions, a reactive non-treponemal test is followed by a confirmatory treponemal test that is specific for Treponema pallidum antibodies. Treponemal tests, while highly specific, typically remain positive for life even after treatment, so they are better suited for confirmation rather than initial screening. PCR isn’t used routinely for screening since it detects bacterial DNA and is less practical for broad surveillance. Therefore, the best initial screening test is a non-treponemal assay such as VDRL.