Rapid Plasma Reagin (RPR/ VDRL)

Description

What is RPR/ VDRL?

The rapid plasma reagin (RPR) test is a blood test that looks for antibodies against a bacterial infection called syphilis. This test doesn’t detect the actual bacteria that cause syphilis. Instead, it looks for antibodies against substances given off by cells that have been harmed by the bacteria.

It is used to screen for active syphilis infection and monitor response to treatment. Non-reactive RPR tests without clinical evidence of syphilis may suggest no current infection or an effectively treated infection. A false positive RPR (means positive results in the absence of syphilis) can be encountered in tuberculosis, malaria, and viral pneumonia. A reactive RPR test suggests past or present infections with the bacteria that cause syphilis. If not detected, syphilis can stay in the body for years and cause harm to internal organs.

Why is RPR/ VDRL done?

• To screen for syphilis in people having symptoms of sexually transmitted infections
• To screen people who are at risk of exposure to syphilis such as having another STD or HIV infection, homosexual men having a sexual partner diagnosed with syphilis, or indulged in high-risk sexual activity
• To screen pregnant women for syphilis
• To monitor the treatment of syphilis

The treatment starts with antibiotics. With this, the level of syphilis antibodies fall and can be checked with another RPR test. Unchanged or rising levels can mean a persistent infection.

What does RPR/ VDRL Measure?

Syphilis is a sexually transmitted disease (STD), caused by the bacteria Treponema pallidum. It is most commonly spread by sexual route (through contact with syphilis sore (Chancre)). Syphilis is easily treatable with antibiotics. However, it can cause severe health problems if left untreated and can be potentially fatal. Maternal transfer to unborn child through an infected mother can cause serious and potentially fatal consequences for the baby.

There are several stages of syphilis:

•       Primary syphilis: Primary stage starts 2-3 weeks after being infected. It usually appears as one or more painless chancres on the sexual partner’s chancre exposed body parts such as on the penis or vagina. Since it is painless, it may go unnoticed, especially if it is in the rectum or on the cervix. It usually disappears within 4-6 weeks even without any treatment.
•       Secondary syphilis: Primary syphilis can progress to secondary syphilis if the infected person is left untreated. The symptoms generally develop from 6 weeks to 6 months after the chancre first appears. It is mainly observed as non-itchy skin rash (rough, red, and spotted), appearing typically on the palms of the hands and the bottoms of the feet. Other associated symptoms could be fever, fatigue, swollen lymph nodes, sore throat, and body aches.
•       Late or tertiary syphilis: Secondary syphilis can progress to late or tertiary stage if it is further left untreated. In this, an infected person may remain without any symptoms (asymptomatic) but continues to have the infection and can last for years. There are various complications associated with tertiary syphilis which can occur if still left untreated such as the bacteria can damage the heart, eyes, brain, central nervous system (Neurosyphilis), bones, joints, or almost any other part of the body. Tertiary syphilis can last for years, with the final stage leading to mental illness, blindness, other neurological problems, heart disease, and death.

Interpreting RPR/ VDRL results

Interpretations

Negative: A negative (“non-reactive”) RPR test result is compatible with a person not having syphilis.

The result of this test can be “positive” or “negative”. But there are some cases where the results can be false positive or false negative.

A negative (“non-reactive”) RPR test result suggests that a person is not having syphilis. However, the body does not always produce antibodies specifically in response to the syphilis bacteria, so the test is not always accurate. False-negatives test result may occur in people with early- and late-stage syphilis. Because of that other tests are required to confirm the results.

A false positive RPR (means positive results in the absence of syphilis) can be encountered in infectious mononucleosis, tuberculosis, leprosy, malaria, lupus erythematosus, vaccinia, and viral pneumonia. Pregnancy, autoimmune diseases, and narcotic addictions may give false-positive results. Also, this test may give false-positive result in pinta, yaws, bejel, and other treponemal diseases.

RPR test is also used to monitor treatment response. Treatment response is generally indicated by a 4-fold (2-tube dilution) reduction in rapid plasma reagin (RPR) titer (e.g., from 1:32 to 1:8). For proper interpretation of RPR results, titers should be obtained using the same testing method and, preferably, at the same testing laboratory.

Failure of nontreponemal test titers to decline 4-fold within 6 months after therapy for primary or secondary syphilis may be indicative of treatment failure. Patients whose titers remain serofast should be reevaluated for HIV infection.