State of the art syphilis diagnostics: rapid point-of-care tests

Abstract

Syphilis remains an important and entirely preventable cause of stillbirth and neonatal mortality. More than 1 million women with active syphilis become pregnant each year. Without treatment, 25% of them will deliver a stillborn baby, 33% will deliver a live low-birth weight baby with an increased chance of dying in the first month of life. Adverse pregnancy outcomes due to syphilis can be prevented by screening pregnant women, and treating those who test positive with a single dose of penicillin before 28 weeks gestation. Until recently access to screening in low- and middle-income countries has been limited, since screening tests have been laboratory based, requiring equipment, electricity and trained laboratory staff. Now a number of rapid, cheap, simple and accurate screening tests are available and can give a result in 15–20 min, enabling those who require treatment to be treated at their first visit.

Keywords::

• congenital syphilis
• point-of-care
• screening
• sexually transmitted infection
• syphilis
• testing

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Syphilis is a treatable bacterial infection. Syphilis remains an important and entirely preventable cause of a range of adverse pregnancy outcomes. More than 1 million women with active syphilis become pregnant each year. Without treatment, 25% of them will deliver a stillborn baby, 33% will deliver a live low birth-weight baby with an increased chance of dying in the first month of life.

• Appropriate diagnostics and early treatment are crucial in preventing long-term complications of syphilis and mother-to-child transmission (MTCT). Screening pregnant women for syphilis is one of the most cost-effective and cost-saving health interventions across a range of syphilis prevalence.

• The diagnosis of syphilis has been a problem in resource-poor settings, which have the highest burden of disease, as the older tests require technical expertise and equipment, which in many cases requires electricity. New rapid, point-of-care (POC) tests are now available, which do not require equipment, can be stored at room temperature and can give a result in 15 min.

• Screening and treatment of pregnant women before 28 weeks gestation will prevent adverse outcomes due to syphilis. The rapid, POC tests are treponemal (TP) tests, which will remain positive for life, and cannot distinguish between active and past treated infection.

• The syphilis POC test, although not perfect, does provide an opportunity for same day testing and treating (STAT) and has been shown to have a beneficial role in a diverse range of healthcare settings.

• Combined TP and non-TP dual POC tests have been developed, which, unlike the TP tests, will enable healthcare workers to distinguish between active syphilis and past, treated infection. This could be the future direction of syphilis testing.

• Quality control is a key part of any program and two approaches to external quality assurance have been piloted in the case of syphilis POC tests.

• The framework and resources that have been made available for HIV PMTCT programs provide an important opportunity for syphilis control programs. The WHO has prioritized the prevention of congenital syphilis. HIV PMTCT programs can combine HIV and syphilis screening, through simple integrated programs, strengthening health systems.

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