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As Congenital Syphilis Epidemic Continues, Stakeholders Work to Expand Rapid Testing


NEW YORK – As the federal government continues to sound the alarm about the congenital syphilis epidemic, stakeholders in the diagnostics industry are encouraging the use of existing rapid tests and development of additional tests to help combat the issue.

Last month, the US Centers for Disease Control and Prevention released data finding that almost 90 percent of congenital syphilis cases in the US in 2022 might have been prevented with timely testing and adequate treatment. From 2012 to 2021, congenital syphilis cases increased 755 percent, while rates of primary and secondary syphilis cases in women of reproductive age increased 676 percent over the same time frame. The skyrocketing rates of syphilis mirror a larger overall trend of increasing rates of sexually transmitted infections in the US. 

The US Department of Health and Human Services has also emphasized the need for action, announcing the creation of a National Syphilis and Congenital Syphilis Syndemic Federal Task Force last month. The task force's mission is to "leverage broad federal resources to reduce rates, promote health equity, and share resources with impacted communities," HHS said in a statement, and it aims to avert 5 percent of congenital syphilis cases by September 2024. 

To do this, it will work directly with jurisdictions to maximize syphilis testing, particularly for pregnant people, and try to expand equitable access to syphilis testing and treatment in communities with limited healthcare resources. 

The task force also aims to promote alternative testing locations for pregnant patients beyond traditional prenatal care settings, such as substance use facilities, harm reduction programs, and emergency departments; educate healthcare providers who work with pregnant patients about emphasizing syphilis testing; promote evidence-based sexual health discussions; and ensure prompt testing and treatment in high-risk counties.

It will also work with health departments to identify counties with high syphilis rates, collaborate on reducing barriers to patient care, and monitor pregnancy status for timely treatment to prevent newborn syphilis, HHS said.

Currently, the CDC recommends screening for syphilis during pregnancy at the first prenatal care visit and again at 28 weeks and delivery for patients who live in communities with high rates of syphilis, are at high risk for syphilis acquisition during pregnancy, or were not previously tested during the pregnancy. 

One of the ways to address this epidemic, the CDC noted in a statement addressing the new data, is the use of rapid syphilis testing and treatment during pregnancy in settings such as emergency departments, syringe service programs, prisons and jails, and maternal and child health programs. 

The current most common practice for syphilis testing involves laboratory-based blood tests, said Jeffrey Klausner, a professor of clinical population and public health sciences at the University of Southern California. There are two kinds of syphilis tests, he added: treponemal tests, which detect antibodies that remain in the body even after effective treatment, and nontreponemal tests, which detect antibodies that indicate current infection.

Using laboratory-based tests, however, means patients have to wait at least a day for results and can miss opportunities for treatment, since they must return to the doctor's office or hospital once the results are in, he said. 

Rapid, CLIA-waived tests have been "transformative" in getting results to patients quickly and ensuring treatment, Klausner said, but one of the challenges is that many providers don't know they exist. 

There are currently two rapid syphilis tests approved by the US Food and Drug Administration that have received CLIA waiver: Syphilis Health Check from Diagnostics Direct and DPP HIV-Syphilis, a combination HIV and syphilis rapid test, from Chembio Diagnostics. Both immunoassays detect Treponema pallidum antibodies in blood and return results in 15 minutes or less. 

Diagnostics Direct CEO Norman Proulx noted that Syphilis Health Check detects both IgG and IgM antibodies. IgG antibodies are longstanding antibodies that every child born to a mother with syphilis will have and do not necessarily mean a baby has been infected, while IgM antibodies indicate a baby has been infected with syphilis. However, the test's results do not differentiate between which antibodies were found in a sample. 

Being unable to differentiate between IgG and IgM antibodies means the tests cannot determine by themselves if an infection is active or old, although in "some ways it doesn't really matter, because if someone's never been treated, they need to be treated immediately, particularly if they're pregnant," Klausner said. However, the inability to distinguish between IgG and IgM antibodies is "one of the major gaps, particularly in newborns that have been born to pregnant women with syphilis," he said. "Even if their syphilis has been treated, you cannot readily determine if the newborn is infected or not."

While there are tests commercialized outside of the US that are IgM-specific, and thus differentiate between active and old infections, those tests aren't available within the US due to the higher regulatory burden — and thus higher cost — of clearing them through the FDA, Klausner said. "It wasn't until recently that people recognized there is this huge burden and there is a market for infant syphilis testing," he added, and many startups don't have the resources to get regulatory approval for their tests from the FDA.

To help solve the problem, Klausner said there is a need for the US government to declare a public health emergency, allowing the FDA to approve Emergency Use Authorizations to bring new IgM detection tests to market with a lower regulatory and financial burden. Declaring a public health emergency would also open opportunities for test development and resource allocation, Klausner said. "We're still not seeing women of reproductive age being routinely tested for syphilis," he said. "There's still a lot of missed opportunities for testing." 

Under a public health emergency, implementing guidelines for routine screening in a variety of settings, including emergency departments and jails, would be easier and could bridge the gap between testing and treatment. 

Elizabeth Finley, director of communications for the National Coalition of STD Directors, said via email that existing screening policies don't extend screening into all of the different places it could be done outside of prenatal care. "We need to start thinking of every medical encounter with a pregnant person as an opportunity to screen for syphilis, and we need to think creatively about other public health encounters — or even home-collect testing — as opportunities to screen," Finley said.

The NCSD would like to see more resources provided to public health jurisdictions and partners so they can be creative in integrating rapid tests into their outreach efforts and disease intervention work, Finley added. "Increasing screening is an urgent need right now, and rapid tests can help us accomplish that."

Multiple research groups and companies are also working on rapid syphilis tests that can detect both treponemal and nontreponemal antibodies. For example, a team from Columbia University has developed a smartphone dongle-based triplex test for HIV, treponemal antibodies, and anti-cardiolipin antibodies as a nontreponemal marker, although it is not commercially available. Chembio Diagnostics also offers its DPP Syphilis Screen and Confirm test in Europe, which detects both treponemal and nontreponemal antibodies, but it has not received FDA approval.

Diagnostics Direct's Proulx said that the company is exploring a potential IgM-specific rapid test for newborns and has begun initial verifications.

Finley also noted the potential impact the FDA's proposed laboratory-developed test rule may have on the issue. The FDA's choice to oversee LDTs "might curtail the development of tests needed for public health," she said. "We need more tests available for syphilis and the STI sector has relied greatly on quick innovation in response to outbreaks." 

"There is a longstanding need for more guidance from FDA to help companies know how to create tests that will be acceptable in the market, but the proposed rule risks the kind of flexible and responsive support public health needs," Finley added.

Irene Stafford, the associate program director for the maternal-fetal medicine fellowship at McGovern Medical School at the University of Texas Health Science Center at Houston, echoed Klausner's thoughts, noting that the current reliance on laboratory tests can miss early infections and increase barriers to care. "The reality is, we might be … testing, but it's very hard for most people to get back into the clinic for treatment," she said.

Barriers to access are particularly prevalent in underserved patient populations, including patients living in poverty and those with substance abuse disorders, who are also disproportionately affected by the syphilis epidemic. To address those issues, Stafford said rapid syphilis diagnostics should be offered "with any opportunity that a patient presents," especially in high-prevalence regions, such as when pregnant patients come into an emergency department. 

One possible issue with implementing rapid tests, Stafford noted, is the additional compliance regulations a CLIA-waived site using point-of-care tests may have to meet, such as different validation requirements. While the tests are reasonably priced — Syphilis Health Check retails for $10 for a box of 20 tests — ensuring compliance can make the tests hard to implement in hospital settings, she said. 

Ultimately, however, the difficulties in implementing rapid testing in certain settings are worth it to ensure syphilis is being treated and prevented in newborns. "Babies don't need to be born with congenital syphilis," she said. "What that tells me is that we have a failure of our healthcare system." 

"Rapid diagnostics need to be implemented in any healthcare setting where a pregnant patient presents and doesn't have care and wasn't tested," she said.