Diagnostic tools for preventing and managing maternal and congenital syphilis: an overview

Syphilis is a major cause of adverse outcomes in pregnancy in developing countries. Fetal death and morbidity due to congenital syphilis are preventable if infected mothers are identified and treated appropriately by the middle of the second trimester. Most pregnant women with syphilis are asymptomatic and can only be identified through serological screening. Non-treponemal tests, such as the rapid plasma reagin (RPR) test, are sensitive, simple to perform, and inexpensive. However, they have often not been available at primary health-care settings because they required cold storage for reagents and electricity to operate a rotator. Additionally, as many as 28% of positive RPR results in pregnant women are biological false positives. Confirmatory assays are usually available only in reference laboratories. Technological advances have resulted in improved serodiagnostic tools for syphilis. New enzyme immunoassays are available for surveillance and for large-scale screening programmes. Decentralized antenatal screening with on-site confirmation is now possible since new RPR reagents that are stable at room temperature have become commercially available, as have solar-powered rotators and simple, rapid point-of-care treponemal tests that use whole blood and do not require electricity or equipment. These will be valuable tools for preventing or eliminating congenital syphilis. The development of a non-invasive rapid treponemal test that distinguishes between active and past infections remains a high priority in areas where syphilis is endemic.