Which screening test is commonly used for syphilis?

The Rapid Plasma Reagin (RPR) test is a non-treponemal screening test commonly used to detect syphilis. It is a blood test that identifies reagin antibodies, which are produced in response to substances released by damaged cells as a result of a syphilis infection.

The RPR test is favored for its quick turnaround time and the ability to process large numbers of samples efficiently, making it a practical option for mass screening. Additionally, it is useful not only for diagnosing syphilis but also for monitoring the treatment progress by tracking changes in antibody levels over time.

In comparison, the Western Blot test is more specific and is usually employed as a confirmatory test rather than a screening tool. Polymerase Chain Reaction (PCR) is a molecular technique that can detect the genetic material of Treponema pallidum, the bacterium that causes syphilis, but it is not typically used as a first-line screening test due to its complexity and cost. The HIV Antibody test specifically screens for HIV infection and is unrelated to syphilis diagnosis.

Thus, the RPR test stands out as the most appropriate first-line screening test for syphilis among the options provided.