What new CDC tests can support a diagnosis of syphilis?

The CDC released updated laboratory recommendations for syphilis testing in 2024 ⁹. These recommendations cover both traditional serologic tests (blood tests that detect antibodies) and newer methods that directly detect the bacteria, Treponema pallidum. While there is no single new test that replaces all others, the CDC now endorses automated serologic tests and molecular tests like nucleic acid amplification tests (NAATs) as part of a diagnostic algorithm ⁹. The goal is to improve accuracy and speed, especially in early infection and congenital syphilis.

What the research says

The CDC's 2024 recommendations emphasize that syphilis diagnosis still requires a combination of two types of serologic tests: nontreponemal tests (which detect antibodies to lipoidal antigens) and treponemal tests (which detect antibodies specific to T. pallidum) ⁹. Newer serologic tests allow for laboratory automation but must be used in an algorithm, which can also involve older manual serologic tests ⁹. For direct detection of the organism, the CDC notes that methods have evolved from microscopic examination of lesion material to molecular detection, such as NAATs ⁹. A 2023 review highlights that NAATs, including transcription-mediated amplification (TMA) and CRISPR-based assays, can bridge the diagnostic 'window period' where traditional serology often fails ⁸. However, these newer tests face standardization hurdles ⁸. Another review notes that while point-of-care tests that detect both treponemal and nontreponemal antibodies would be a huge step forward, they are not yet widely available in the U.S. ¹⁰. The CDC also acknowledges that limited point-of-care tests are available in the United States, and increased availability could expand screening and reduce time to treatment ⁹.

What to ask your doctor

• What type of syphilis test are you using — a nontreponemal test, a treponemal test, or both?
• If I have a lesion, would a molecular test (like a NAAT) be more accurate than a blood test?
• Are the newer automated serologic tests available at this lab, and how do they compare to older manual tests?
• Could a point-of-care test be an option for me to get faster results?
• If I have been treated for syphilis before, how will you tell if this is a new infection or a past one?