Key points
Economic analysis shows rapid testing is cost effective and can fast-track treatment
Three testing algorithms varied in cost effectiveness and accuracy
In pregnant women, the risk of false positives is outweighed by the risk of not making tests available
Researchers from Monash University and Alfred Health's Melbourne Sexual Health Centre are advocating for greater use of rapid tests for syphilis, saying it stacks up both economically and in health outcomes – especially in women of reproductive age.
The researchers investigated the economic value of syphilis Rapid Diagnostic Tests (RDTs) in pregnant women, and men who have sex with men (MSM). RDTs enable same-day diagnosis and treatment, while traditional lab-based tests (which use a finger prick or a needle), although more accurate, can leave patients waiting days to weeks for a result.
It comes amid soaring worldwide and domestic infections which, in August, prompted Chief Medical Officer Professor Michael Kidd to declare syphilis a Communicable Disease Incident of National Significance. Congenital syphilis has resulted in a score of newborn deaths in Australia in recent years; surviving babies often have impaired brain development, hearing and vision.
The Monash-Alfred study, published in The Lancet Infectious Diseases, evaluated three rapid testing algorithms (or pathways), based on the two main types of rapid tests available. They compared cost, number of active cases missed, and instances of overtreatment, taking into account disease prevalence at a population level.
First author Ying Zhang, from the Monash University School of Translational Medicine and the Melbourne Sexual Health Centre said rapid testing's brief history meant there was little guidance for clinicians.
"The first rapid test for syphilis alone was approved in 2020, so this work is filling a knowledge gap about what works best for different groups, and getting the balance right between overtreatment and missing cases, based on the epidemiology," Ms Zhang said. "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."
The researchers found that In pregnant women, the simplest and cheapest test (T-RTD) worked best. "T-RTD can't distinguish between an old infection that no longer needs treatment, and a new active infection," Ms Zhang said. "But the impact of missing a syphilis case in pregnancy is so extreme that overtreatment is a lesser evil."
Conversely, a modified version of the dual T/NT-RTD test ("dual" because it can confirm infection at either one of two points in the testing process) performed better on cost and in health outcomes when used in populations with higher prevalence, such as MSM in urban areas. "We found a substantial reduction in missed cases of more than 90 per cent using this algorithm. Urban clinics tend to have better triage and follow-up care, so they can more easily mitigate the impact of overtreatment," Ms Zhang said.
The higher precision of this algorithm also meant less likelihood of overtreatment. "You can get syphilis more than once, so we want to avoid overuse of antibiotics, which of course contributes to resistance."
Senior author and Melbourne Sexual Health Centre Director, Professor Jason Ong, said rising syphilis incidence showed that a one-size-fits-all approach isn't working. "In pregnancy, a simpler test that may treat a few extra people unnecessarily is better than missing an infection that could harm a baby. But for men at higher risk, using a test that's more precise helps avoid unnecessary treatment while still finding most cases," he said.
"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. "Lab tests are the gold standard in syphilis testing, but time is critical, especially for pregnant women. And in settings where access to labs and healthcare is difficult, rapid tests should be the first-line option."
Read the research paper: https://doi.org/10.1016/S1473-3099(25)00588-2
