First Comprehensive Syphilis Test to Definitively Diagnose Active Infection In 10 Minutes

Syphilis, which can be transmitted sexually or from mother to infant during birth, is a treatable infection, but only if diagnosed early. If left untreated, syphilis can advance from painless sores to severe damage in the brain and cardiovascular system. Despite being first documented over 500 years ago — with some experts suggesting it may have affected humans for thousands of years — there is still no fast, reliable test to detect active syphilis infection. The disease often mimics symptoms of various other sexually transmitted and infectious conditions, making it challenging to diagnose and treat. Now, a collaborative project is working on a one-step confirmatory laboratory test designed to definitively diagnose active syphilis infection in just 10 minutes.

Accurately diagnosing syphilis requires identifying a range of symptoms, reviewing medical and sexual history, and performing several lab tests. When a person is infected, the body produces antibodies to fight the bacterium Treponema pallidum, which causes syphilis. These antibodies are produced whether the person is showing symptoms or not. Known as treponemal-specific antibodies, they can remain in a person’s system for decades, even if the infection is never active or after it has been successfully treated, making them unreliable for detecting an active infection. The body may also produce non-treponemal antibodies in response to active infection; however, this reaction is not exclusive to syphilis, so doctors must test for both types of antibodies to make a more accurate diagnosis and choose an appropriate treatment. While there are only two FDA-approved syphilis rapid tests, these detect only treponemal-specific antibodies, which could be from an infection that was treated years ago.

To definitively diagnose an active syphilis infection and determine the best treatment, clinicians need to test for non-treponemal antibodies that signal current infection, ideally obtaining semi-quantitative results. This involves counting the number of antibodies in a blood sample, a process that typically takes two to seven days and requires specialized equipment, meaning the tests are generally sent to a lab rather than being done in the doctor’s office. This approach is necessary to ensure high sensitivity and low false-positive rates when determining appropriate treatment. Researchers from The Pennsylvania State University (University Park, PA, USA) are now developing a platform that combines treponemal and non-treponemal assays to offer a more definitive, stand-alone diagnosis of syphilis.

The proposed platform utilizes highly sensitive electrochemical sensors that detect changes in current caused by the interaction between both types of antibodies and biological materials released from the bacterium or damaged host cells. The sensors are made from graphene, an atomically thin material that is highly responsive to these changes. These sensors can detect and quantify various proteins or molecules linked to these interactions. In initial tests using commercially available blood serum samples, the researchers found that the sensors could detect both antibody types in less than 10 minutes with high sensitivity. Once testing and refinement of their platform are complete, the team plans to develop a blood sample extraction device paired with a simple reader, similar to an at-home glucose meter, which will provide results in 10 minutes.

“This is the first study using electrochemical sensor for an integrated assay — or comprehensive test to detect multiple targets — for highly sensitive, rapid, point-of-care detection of both treponemal and non-treponemal antibodies needed to accurately diagnose active syphilis infection,” said Penn State Professor Dipanjan Pan. “Our goal is to simultaneously detect and quantify these antibodies, identifying and diFfferentiating active from past cases of syphilis within 10 minutes to fulfill an urgent, unmet global need.”