Syphilis RPR

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Also known as: RPR Monitor with Reflex to Titer, Syphilis

Rpr (Monitor)

RPR (rapid plasma reagin) is a screening test for syphilis. It looks for antibodies that are present in the blood of people who have the disease.
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The Syphilis RPR test contains 1 test with 1 biomarker.

Brief Description: The rapid plasma reagin test is used to determine if a person has been infected with syphilis. An RPR can be used to monitor treatment for syphilis and the effectiveness of syphilis treatment. Syphilis testing is a two-part test. The first round of testing for syphilis is an RPR test. If these results come back positive, a second round of testing will be required. A positive RPR result will be followed by a second method that will be used to confirm the results. If the second syphilis test comes back positive, the affected person will be diagnosed with syphilis. If the second test comes back negative, it could mean that the first test is a false positive and more testing may be necessary.

Also Known As: Rapid Plasma Reagin with Reflex to Titer, Syphilis RPR, Syphilis Titer test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required


A positive RPR screen must be followed by a specific treponemal antibody test (e.g., FTA-ABS):

A positive result on the second method confirms the screening result and the affected person is diagnosed with syphilis.

A negative result on the treponemal test may mean that the initial RPR test was falsely positive. Further testing and investigation may be done to determine the cause of the false positive.


False-positive results have been associated in patients with infections, pregnancy, autoimmune disease, old age, Gaucher disease, and malignancy.

When is a Syphilis RPR test ordered?

A Syphilis RPR test may be ordered in the following situations:

  1. Routine Screening: It is commonly included in routine sexually transmitted infection (STI) screenings, especially for individuals at higher risk, such as those with multiple sexual partners or a history of unprotected sex.

  2. Symptoms of Syphilis: When a person presents with signs and symptoms suggestive of syphilis, such as sores (chancre) on the genitals, skin rash, swollen lymph nodes, or unexplained fevers, an RPR test is ordered to confirm or rule out the infection.

  3. Pregnancy: Pregnant women are often screened for syphilis as part of routine prenatal care. Syphilis can be transmitted from a mother to her unborn child, potentially leading to severe complications. Early detection and treatment are crucial to prevent transmission to the fetus.

What does a Syphilis RPR blood test check for?

Syphilis is a bacterial infection caused by Treponema pallidum that is primarily spread during sexual activity, such as by direct contact with a syphilis sore. The majority of common syphilis tests can detect antibodies in the blood that were produced in response to a T. pallidum infection. Some less common methods can be used to locate the bacterium or its genetic components.

Syphilis is easily treated with medications, but if left untreated, it can cause serious health concerns. A mother who is afflicted can convey the disease to her unborn child, which can have serious and even fatal effects for the newborn.

With syphilis, there are numerous stages that can occur:

  • The primary stage of syphilis begins about 2-3 weeks following infection. One or more chancres emerge, usually on the body portion exposed to the chancre of the sexual partner, such as the penis or vaginal area. The chancre, on the other hand, is usually painless and may go unnoticed, especially if it is in the rectum or on the cervix, and it goes away within 4-6 weeks, mending whether or not the infected person is treated.
  • If primary syphilis is left untreated, secondary syphilis can develop anywhere from 6 weeks to 6 months after the chancre initially emerges. It is characterized by a rough, red, and speckled skin rash that appears regularly on the palms of the hands and the bottoms of the feet and does not itch. Fever, weariness, enlarged lymph nodes, sore throat, and body aches are some of the other symptoms that can occur.
  • Secondary syphilis can progress to a latent stage, during which an infected individual has no symptoms but still retains the infection, and this stage can remain for years if left untreated. If left untreated, roughly 15% of persons will develop late, or tertiary, syphilis issues. Bacteria can harm the heart, eyes, brain, neurological system, bones, joints, and practically any other component of the body in these situations. Neurosyphilis is a disease that affects the central nervous system. Tertiary syphilis can linger for years, leading to mental illness, blindness, other neurological issues, heart disease, and death in the ultimate stage.
  • If left untreated, syphilis progresses.

The basic and secondary stages of syphilis are the most contagious. About a third of the approximately 63,000 new cases of syphilis reported to the CDC in 2014 were main or secondary stage syphilis. Eighty-three percent of these cases included guys having intercourse with other men.

Antibiotics, usually penicillin, can be used to cure syphilis. Infections that have been acquired recently can be rapidly healed; however, someone who has been infected for more than a year may require prolonged therapy.

Lab tests often ordered with a Syphilis RPR test:

When an RPR test is ordered, it's often part of a broader evaluation for sexually transmitted infections (STIs) or related conditions. Here are some tests commonly ordered alongside it:

  1. FTA-ABS:

    • Purpose: To confirm the presence of antibodies specifically against Treponema pallidum, the bacteria that causes syphilis.
    • Why Is It Ordered: RPR is a non-treponemal test and can give false-positive results; confirmatory treponemal testing is needed to confirm a diagnosis of syphilis.
  2. Chlamydia and Gonorrhea Tests:

    • Purpose: To test for chlamydia and gonorrhea, which are common bacterial STIs.
    • Why Is It Ordered: These STIs often occur together with or present similarly to syphilis, so testing for them is usually part of a comprehensive STI screening.
  3. Hepatitis B and C Tests:

    • Purpose: To screen for hepatitis B and C viruses, which can be transmitted sexually or through blood.
    • Why Is It Ordered: To assess for co-infection, as hepatitis can have serious health implications and may affect the management of syphilis.
  4. Complete Blood Count (CBC):

    • Purpose: Provides a broad picture of overall blood health.
    • Why Is It Ordered: To assess general health status and detect any signs of infection or other health issues.
  5. Herpes Simplex Virus (HSV) Types 1 and 2 Serology:

    • Purpose: To test for antibodies to the herpes simplex virus, which causes oral and genital herpes.
    • Why Is It Ordered: To diagnose herpes infection, as symptoms can sometimes be confused with syphilis.

These tests, when ordered alongside an RPR test, provide a comprehensive view of an individual’s STI status and overall health. They are critical for accurately diagnosing syphilis, assessing for co-infections, and guiding appropriate treatment. The specific combination of tests will depend on the individual's risk factors, symptoms, and clinical history.

Conditions where a Syphilis RPR test is recommended:

A Syphilis RPR test may be required in the following conditions or situations:

  1. Routine STI Screening: Routine screening for sexually transmitted infections, including syphilis, is recommended for individuals with multiple sexual partners, those engaging in unprotected sex, or individuals at increased risk based on their sexual history.

  2. Symptoms of Syphilis: When a person presents with signs and symptoms consistent with syphilis, such as genital sores, skin rash, swollen lymph nodes, or unexplained fevers, an RPR test is ordered to confirm or rule out the infection.

  3. Pregnancy: Syphilis screening is a routine part of prenatal care to detect and treat the infection in pregnant women. Early detection and treatment can prevent transmission to the fetus, which can lead to congenital syphilis with potentially severe consequences

How does my health care provider use a Syphilis RPR test?

Syphilis tests are used to detect and/or diagnose infection with the bacterium Treponema pallidum, which causes syphilis.

There are a variety of tests to choose from. The most common type of test is an antibody test.

Antibody tests identify antibodies in the blood and, occasionally, in the cerebrospinal fluid. Nontreponemal antibody test and treponemal antibody test are the two types of syphilis tests available. Syphilis screening can be done with any type, but it must be followed by a second test that employs a different approach to confirm a positive result and identify active syphilis:

Antibodies that aren't specifically directed towards the Treponema pallidum bacterium are detected by nontreponemal antibody testing. The body produces these antibodies when a person has syphilis, but they can also be produced in a variety of other situations. Because the tests are non-specific, false-positive findings can be produced by things like IV drug usage, pregnancy, Lyme disease, certain types of pneumonia, malaria, tuberculosis, or certain autoimmune disorders like lupus. A positive screening result must be double-checked with a more detailed test. Nontreponemal testing include the following:

RPR—in addition to screening, this test can be used to track syphilis therapy. Antibody levels are tested for this reason. When an initial test for treponemal antibodies is positive, it can also be used to confirm the existence of an active infection.

VDRL—in addition to blood, this test is largely used to identify neurosyphilis in the CSF.

Antibodies to T. pallidum are detected by treponemal antibody tests, which are blood tests. Because they are extremely specific for syphilis, they are unlikely to produce a positive result in other diseases. Once a person is infected and these antibodies form, they remain in the bloodstream for the rest of their lives. Nontreponemal antibodies, on the other hand, usually vanish within 3 years in a properly treated person. As a result, a positive treponemal screening result must be followed by a nontreponemal test in order to distinguish between an active infection and one that has been successfully treated in the past. FTA-ABS is a treponemal antibody test that is beneficial after the first 3-4 weeks after exposure. It can be used to assess antibodies to T. pallidum in the CSF to assist diagnose neurosyphilis in addition to blood testing.

  • TP-PA—instead of FTA-ABS, this test is sometimes used because it is more specific and has less false positives.
  • Another confirmatory approach is MHA-TP, which is presently used considerably less frequently.
  • Immunoassays—Several automated tests have been developed in recent years, making them useful for screening applications.

What do my Syphilis test results mean?

A negative blood test indicates that there is most likely no infection. A negative screening test, on the other hand, simply states that there was no evidence of disease at the time of the test. Antibodies may not be detected for several weeks following bacterial contact. If a person is aware that he or she has been exposed, or if the risk of infection remains high, additional testing may be required. It is also critical for persons who are at a higher risk of contracting syphilis to get regular screening tests to check for infection.

A particular treponemal antibody test must be performed after a positive RPR or VDRL screen:

The infected person is diagnosed with syphilis once a positive result on the second method confirms the screening result.

A negative treponemal test result could indicate that the initial RPR or VDRL test was incorrectly positive. To discover the reason of the false positive, more testing and investigation may be conducted.

A treponemal antibody test, on the other hand, will be used as an initial test by a healthcare practitioner or laboratory. A positive result indicates the presence of syphilis antibodies in the blood, but because treponemal antibodies stay positive even after an infection is treated, it does not indicate whether the person is now afflicted or has previously been infected. Nontreponemal antibodies found with an RPR, on the other hand, usually vanish after 3 years in a properly treated person. If the initial treponemal test is positive, an RPR can be used to determine whether the infection is active or past. A positive RPR in this scenario would establish that the person has been exposed to syphilis and, if not previously treated, has an ongoing infection or, if treatment occurred more than 3 years ago, possible re-infection.

The results of one or more RPR titers may be used to monitor treatment and/or determine if treatment was successful. Antibodies to syphilis should be decreased after therapy. If the RPR was 1:256 before therapy, a number of 1:16 after treatment would indicate a reduced amount of antibody. The affected person may have a persistent infection or was reinfected if the titer stays the same or rises. The results can also be transformed to a whole number or reported as dilutions.

Nontreponemal antibodies fade away over time after effective treatment, whereas treponemal antibodies remain in the blood for the rest of one's life.

Most Common Questions About the Syphilis RPR test:

Understanding the Syphilis RPR Test

What is the Syphilis RPR test?

The Syphilis Rapid Plasma Reagin (RPR) test is a blood test used to screen for syphilis, a sexually transmitted infection caused by the bacterium Treponema pallidum.

Why is the Syphilis RPR test ordered?

This test is commonly ordered when a patient presents symptoms of syphilis, has had sexual contact with a person known or suspected to have syphilis, or is being screened during pregnancy. It is also used for people who are at high risk of getting syphilis, such as those with multiple sexual partners or those who are HIV positive.

Interpreting Syphilis RPR Test Results

What does a positive Syphilis RPR test result mean?

A positive RPR test suggests that a person has been infected with the syphilis bacterium. However, false positives can occur, so a positive result is typically confirmed with a more specific test for syphilis, such as a fluorescent treponemal antibody-absorption (FTA-ABS) test or a Treponema pallidum particle agglutination assay (TP-PA).

What does a negative Syphilis RPR test result mean?

A negative RPR test generally suggests that a person does not have a current syphilis infection. However, the test may not detect syphilis in the very early stage of infection, before the body has had time to develop antibodies.

What is the significance of the titer value in a Syphilis RPR test?

The titer value in an RPR test provides a semi-quantitative measure of antibodies present. In treatment monitoring, a falling titer indicates a response to therapy, while a rising titer could indicate a new infection or treatment failure.

Syphilis RPR Test and Medical Conditions

Can the Syphilis RPR test diagnose other conditions apart from syphilis?

While the RPR test is primarily used to diagnose syphilis, it can sometimes provide positive results in non-syphilis conditions like lupus or Lyme disease. These are considered false-positive results.

How does the Syphilis RPR test relate to HIV testing?

Syphilis and HIV are both sexually transmitted diseases, and individuals with one are often tested for the other due to increased risk. In some cases, HIV can complicate the interpretation of syphilis test results.

General Queries about the Test

How does the Syphilis RPR test differ from the Syphilis FTA-ABS test?

The RPR test is a non-treponemal test that looks for non-specific antibodies that your body produces while fighting syphilis. The FTA-ABS test is a treponemal test that looks for antibodies that are specific to the bacterium that causes syphilis. It is usually used to confirm a positive RPR result.

Can medications affect the Syphilis RPR test?

Antibiotic treatment can affect the results of an RPR test, particularly if taken during early stages of syphilis infection.

Why isn't the Syphilis RPR test used as the sole method for diagnosing syphilis?

The RPR test has the potential for both false positives and false negatives. Therefore, positive results are usually confirmed with a more specific treponemal test for syphilis.

How does pregnancy affect the Syphilis RPR test?

Pregnant women are routinely screened for syphilis using the RPR test due to the serious risk syphilis poses to the fetus. Pregnancy itself doesn't affect the RPR test result, but untreated syphilis can lead to stillbirth, neonatal death, or infant disorders.

Can the Syphilis RPR test predict the risk of developing syphilis?

No, the RPR test can only indicate a current or past syphilis infection. It cannot predict the risk of developing syphilis in the future.

Can the Syphilis RPR test be used to monitor treatment for syphilis?

Yes, the RPR test is often used to monitor the effectiveness of syphilis treatment. A decrease in RPR titer is typically seen with successful treatment.

How does the Syphilis RPR test relate to congenital syphilis?

Pregnant women with untreated syphilis can pass the infection to their babies, leading to congenital syphilis. The RPR test is used to screen for syphilis in pregnant women to prevent this occurrence.

Can the Syphilis RPR test be used to evaluate infertility issues?

Syphilis can cause complications that lead to miscarriage or stillbirth, but the RPR test itself is not used as a diagnostic tool for infertility. However, it may be part of the overall testing in the evaluation of repeated pregnancy losses.

How does the Syphilis RPR test relate to neurosyphilis?

Neurosyphilis refers to an infection involving the central nervous system. While the RPR test can suggest the presence of a syphilis infection, it cannot specifically diagnose neurosyphilis. Additional tests, such as a spinal fluid examination, are needed for such a diagnosis.

Can the Syphilis RPR test help in understanding cardiovascular symptoms?

Syphilis can in some cases affect the cardiovascular system (cardiovascular syphilis), leading to symptoms like chest pain or shortness of breath. While the RPR test can suggest a syphilis infection, it cannot directly diagnose cardiovascular involvement.

How do other sexually transmitted diseases (STDs) affect the Syphilis RPR test results?

The presence of other STDs doesn't typically affect the RPR test result. However, individuals with one STD, such as syphilis, often get tested for other STDs, including HIV, due to common risk factors.

Can the Syphilis RPR test be used in the detection of late-stage syphilis?

Yes, the RPR test can help detect late-stage syphilis. However, in the later stages of infection, the test may occasionally yield false-negative results.

Does the Syphilis RPR test help in determining the severity of a syphilis infection?

The RPR test does not directly measure the severity of syphilis infection, but a high titer might suggest a more active or extensive disease.

How does age affect the Syphilis RPR test results?

Age in itself doesn't affect the RPR test results. However, sexual activity and risky behavior, which can vary with age, can influence the risk of having a syphilis infection.

How do general health conditions impact the Syphilis RPR test?

Certain health conditions like lupus or HIV, as well as pregnancy, can affect the immune system and potentially cause false-positive RPR results.

Can the Syphilis RPR test help in understanding mental health disorders?

Neurosyphilis can sometimes cause symptoms such as changes in personality or psychosis. While the RPR test can suggest a syphilis infection, it cannot directly diagnose neurosyphilis or link syphilis to mental health disorders.

Can the Syphilis RPR test be influenced by a person's lifestyle?

Risky sexual behavior, such as having unprotected sex or multiple sexual partners, can increase the likelihood of a positive RPR test due to increased risk of syphilis infection.

Can the Syphilis RPR test help in diagnosing other types of treponemal diseases?

The RPR test is a non-treponemal test and isn't specific to the bacterium that causes syphilis. Therefore, it cannot definitively diagnose other treponemal diseases. However, false positives can occur with certain other infections.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.

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