Improved point-of-care test to eliminate congenital syphilis

This project aimed to optimise and validate an innovative, specific and sensitive point-of- care (POC) test, which, for the first time, would rapidly and accurately diagnose active syphilis and allow for immediate treatment at the point of care. This diagnostic test would result in significant improvements in the health of women and children through prevention of stillbirths and severe neonatal morbidity and mortality associated with congenital syphilis.

A test that could rapidly and accurately diagnose active syphilis at the point-of-care would lead to timely diagnosis and immediate treatment of pregnant women, thereby substantially reducing stillbirths and neonatal morbidity and mortality.

2014-2018

This new POC test was simple to use, instrument free and only needed a finger-prick sample of blood. It produced accurate results within 30 minutes. It was a disposable, low-cost lateral flow test with proven manufacturing processes and being similar to other point-of- care tests already familiar to health care workers, requiring minimal training and readily applicable to primary health care facilities.

We aimed to develop the first POC test to allow specific diagnosis of active syphilis infection at the point-of-care, which would minimise loss to follow-up and maximise effective treatment.

Activities:
This project involved developing a new optimised POC test that detects a novel biomarker present during active syphilis infection and IgG (present for life after syphilis infection) separately in a single device and would therefore be able to differentiate active from past or treated infections.

The new test was optimised and validated in the laboratory against standard syphilis serology – RPR and TPHA – as well as a commercial laboratory assay (ELISA). The specificity and sensitivity were assessed using a panel of approximately 60 plasma samples representing active syphilis (n=20), past syphilis (n=20) and healthy controls (n=20) obtained from the National Serology Reference Laboratory in Melbourne, Australia. Following the laboratory- based test optimisation, initial performance was evaluated in a “blinded” study using an independent panel of stored plasma samples (n=450, NCSTDs, China; n=300, OPHID, Zimbabwe).

The new syphilis test was compared with standard syphilis serology, an ELISA and three of the available syphilis POC tests. Positive and negative predictive values were calculated for populations with different prevalence levels, demonstrating the potential of this new POC test to prevent congenital syphilis.

Results
The primary outcome of this study is the successful development of a point-of-care syphilis test with comparable sensitivity and specificity to available rapid syphilis diagnostic tests, and the ability to accurately distinguish between active and past treated infections. This test could result in immediate access to diagnosis and significantly increased syphilis treatment uptake, thereby improving maternal and neonatal health outcomes and reducing stillbirths.

Read the publication here.