CDC Publishes First Comprehensive Testing Recommendations for Syphilis

ATLANTA — The Centers for Disease Control and Prevention has published its first-ever comprehensive recommendations for laboratory testing for syphilis.

The new guidance was published in the agency’s Morbidity and Mortality Weekly Report last Thursday.

Among other things, it includes “approaches for laboratory-based tests, point-of-care tests, sample processing and how laboratories should report test results to clinicians and health departments.” 

While the recommendations are primarily intended for clinical laboratory or disease control personnel, they are also geared to helping clinicians understand how to collect and process specimens, interpret test results and counsel and treat patients, the CDC said.

Until now, testing for syphilis has largely been based on serologic algorithms to detect a humoral immune response to Treponema pallidum, which causes the systemic bacterial infections. 

Traditionally, these tests have been divided into two categories — nontreponemal tests, which detect antibodies that are broadly reactive to lipoidal antigens shared by both host and T. pallidum and treponemal tests, which detect antibodies specific to T. pallidum. 

The two tests must be used together to distinguish between an untreated infection or a past infection that has been successfully treated,according to a summary included with the new recommendations..

Newer serologic tests allow for laboratory automation but must be used in an algorithm, which also can involve older manual serologic tests.

Direct detection of T. pallidum continues to evolve from microscopic examination of material from lesions for visualization of T. pallidum to molecular detection of the organism.

Right now, officials with the CDC said, there are limited point-of-care tests for syphilis available in the United State.

“Increased availability of point-of-care tests that are sensitive and specific could facilitate expansion of screening programs and reduce the time from test result to treatment,” they wrote. 

According to the CDC, the United States is currently in the midst of a syphilis epidemic, with cases having risen nearly 80% between 2018 and 2022 and congenital cases up 183% during the same period.

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