Monash University study finds different testing algorithms work best for pregnant women versus men who have sex with men.
New research from Monash University and Alfred Health’s Melbourne Sexual Health Centre shows that rapid diagnostic tests for syphilis offer significant economic and health benefits, particularly for pregnant women and men who have sex with men, compared to traditional laboratory-based testing methods.
The study, published in The Lancet Infectious Diseases, evaluated three rapid testing algorithms based on the two main types of rapid tests available, comparing cost, number of active cases missed, and instances of overtreatment while accounting for disease prevalence at the population level.
Rapid diagnostic tests enable same-day diagnosis and treatment, while traditional lab-based tests, though more accurate, can leave patients waiting days to weeks for results. The research comes as syphilis infections surge worldwide and domestically, prompting Australia’s chief medical officer to declare syphilis a Communicable Disease Incident of National Significance in August.
Different Tests for Different Populations
The researchers found that the simplest and least expensive test, T-RTD, worked best for pregnant women, despite its inability to distinguish between old and new infections.
“T-RTD can’t distinguish between an old infection that no longer needs treatment and a new active infection,” says Ying Zhang, from the Monash University School of Translational Medicine and the Melbourne Sexual Health Centre and the study’s lead author. “But the impact of missing a syphilis case in pregnancy is so extreme that overtreatment is a lesser evil.”
For populations with higher prevalence, such as men who have sex with men in urban areas, a modified version of the dual T/NT-RTD test performed better on cost and health outcomes. This algorithm showed a reduction in missed cases of more than 90%.
“Urban clinics tend to have better triage and follow-up care, so they can more easily mitigate the impact of overtreatment,” says Zhang. The higher precision of this algorithm also reduced the likelihood of overtreatment, helping avoid overuse of antibiotics that contributes to resistance.
Addressing Rising Infection Rates
Congenital syphilis has resulted in multiple newborn deaths in Australia in recent years, with surviving babies often experiencing impaired brain development, hearing, and vision problems.
“In pregnancy, a simpler test that may treat a few extra people unnecessarily is better than missing an infection that could harm a baby,” says Jason Ong, senior author and Melbourne Sexual Health Centre director. “But for men at higher risk, using a test that’s more precise helps avoid unnecessary treatment while still finding most cases.”
The study addresses a knowledge gap in rapid syphilis testing guidance for clinicians. The initial rapid test for syphilis alone was approved in 2020, leaving limited evidence-based recommendations for different patient populations.
“Confirming an active syphilis case can be difficult—especially when we don’t have a patient’s medical history—and tests don’t tell the whole story,” says Zhang.
Implementation Recommendations
The researchers emphasize that while laboratory tests remain the gold standard for syphilis testing, time is critical, especially for pregnant women. In settings where access to labs and healthcare is difficult, rapid tests should be the first-line option.
“The next step is making sure these tests are available where they’re most needed—especially in antenatal care and for communities with higher infection burden—so we can save lives and stop the rise in cases,” says Ong.
The study evaluated algorithms based on disease prevalence, cost-effectiveness, and clinical outcomes to provide evidence-based guidance for implementing rapid syphilis testing in different healthcare settings and patient populations.
ID 88951614 © ibreakstock | Dreamstime.com
