The Rapid Plasma Reagin (RPR) test is a routine blood screening performed during pregnancy. It detects antibodies produced by the body in response to certain infections. The RPR test plays a role in prenatal care by helping to identify a specific infection that could significantly affect both the pregnant individual and the developing fetus. It measures non-specific antibodies and serves as an initial indicator for potential health concerns, allowing for early identification and intervention, rather than a definitive diagnosis.
What the RPR Test Screens For
The RPR test specifically screens for syphilis, a bacterial infection caused by Treponema pallidum. This infection is a concern during pregnancy because it can cross the placenta from the pregnant person to the developing fetus. Untreated syphilis in pregnancy can lead to severe complications, including miscarriage, premature birth, stillbirth, and infant death. It can also cause serious, lifelong health problems for the baby, impacting organs like the brain, eyes, and bones.
Due to these potential risks, the RPR test is a standard and routine part of prenatal care. Early detection through screening allows healthcare providers to intervene promptly, significantly reducing the likelihood of adverse outcomes for both the pregnant individual and the baby.
Interpreting RPR Test Results
A “negative” RPR result indicates that no evidence of an active syphilis infection was detected at the time of the test. This means the body is not currently producing the non-specific antibodies associated with an active infection.
A “positive” or “reactive” RPR result, however, suggests the presence of these antibodies, indicating a current or past infection with syphilis. The RPR test measures non-specific antibodies and is not exclusive to syphilis. The result may also be reported with a “titer,” such as 1:8 or 1:16. This titer indicates the concentration of antibodies in the blood; higher titers generally suggest a more active infection, but even a low titer can be significant.
The possibility of “false positives” is an important consideration with RPR tests. A false positive occurs when the test indicates a positive result, but the individual does not have an active syphilis infection. Common reasons for false positives include other infections, such as Lyme disease, autoimmune conditions like lupus, or even pregnancy itself. Therefore, a positive RPR test always requires further, more specific confirmation to determine the true status of the infection.
Next Steps After a Positive Result
If an RPR test returns a positive result during pregnancy, the immediate next step involves confirmatory testing. These include treponemal tests like the Treponema pallidum particle agglutination (TP-PA) test or the fluorescent treponemal antibody absorption (FTA-ABS) test. These tests specifically detect antibodies against the syphilis bacterium itself, helping distinguish between an active infection, a previously treated infection, or a false positive.
If the confirmatory tests confirm an active syphilis infection, treatment is initiated promptly. Penicillin is the standard and most effective treatment for syphilis during pregnancy. It is highly effective and safe for both the pregnant person and the fetus, and is the only known antimicrobial that can effectively treat fetal infection and prevent congenital syphilis. Even in cases of penicillin allergy, desensitization to penicillin is recommended, followed by penicillin treatment, as no proven alternatives are available for treating syphilis in pregnancy.
After treatment, follow-up RPR tests are conducted to monitor the response to therapy. A significant decrease in the RPR titer indicates effective treatment; a fourfold decrease, for example, confirms success. If titers do not decrease as expected or if they rise, it may indicate treatment failure or reinfection, requiring further evaluation and potential retreatment. Healthcare providers also discuss partner notification, advising the pregnant individual to inform their sexual partners so they can also be tested and treated. This helps prevent reinfection and further spread.
Preventing Congenital Syphilis
The overarching goal of RPR testing in pregnancy is to prevent congenital syphilis. This condition occurs when the syphilis bacterium is passed from a pregnant person to their baby during pregnancy or at birth. If left untreated, this condition can lead to severe health consequences for the infant, including birth defects, developmental delays, vision and hearing problems, and even death.
Early and consistent prenatal care, which includes timely RPR screening, is the primary method to prevent congenital syphilis. Screening all pregnant individuals at their first prenatal visit, and again at 28 weeks’ gestation and at delivery for those at high risk, allows for early detection and intervention. When syphilis is identified early in pregnancy and treated appropriately with penicillin, the risk of passing the infection to the baby is significantly reduced. This early detection and treatment can largely eliminate the devastating effects of congenital syphilis, safeguarding the health of newborns.