Get up to 40% Off on Select Immune Products 90-Day Supply Get up to 40% Off on Select Immune Products 90-Day Supply


How Do You Test for Syphilis?

Fact Checked

sad pregnant woman

Story at-a-glance -

  • People can undergo two tests to learn if they have syphilis or not. The two tests are nontreponemal tests and treponemal tests
  • Treponemal antibodies are known to appear earlier than nontreponemal antibodies, and remain detectable for life, even after successful treatment

You can undergo two types of tests to learn if you have syphilis: nontreponemal tests and treponemal tests. Both look for antibodies in the blood and sometimes in the cerebrospinal fluid (CSF).1 If you are exhibiting symptoms of syphilis, you need to take both tests to determine an accurate diagnosis.2

What Are Nontreponemal Tests?

Nontreponemal syphilis tests are simple and inexpensive tests that look for antibodies, but they don't specifically target the Treponema pallidum bacteria responsible for this STD. While the antibodies appear in people with syphilis, they may also show up because of another disease, giving a false positive result. Therefore, the two types of nontreponemal tests and the antibody titer results must be interpreted through a combination of factors:3,4

  • Rapid Plasma Reagin (RPR) — An RPR may be useful alongside screening to determine syphilis treatment. This can be utilized to see if an active infection is present once an initial test for treponemal antibodies yields a positive result.
  • Venereal Disease Research Laboratory (VDRL) — A VDRL, in conjunction with a blood test, is done on the CSF. It aims to diagnose another type of syphilis called neurosyphilis.

However, nontreponemal tests have caveats. The Centers for Disease Control and Prevention (CDC) notes that both tests aren't enough to fully diagnose syphilis and, as mentioned, may produce false-positive results. Because of this, a treponemal test must be done to ensure a positive screening result. Taking a nontreponemal test before a treponemal test is known as the "classical" testing algorithm.5

What Are Treponemal Tests?

These are diagnostic tests that check for antibodies specific to syphilis, which appear before nontreponemal antibodies. Because treponemal antibodies can remain in your blood for the duration of your life, they can be detected easily, even if you were treated for the infection. Four types of treponemal tests may be recommended:6,7,8

  • Fluorescent Treponemal Antibody Absorption (FTA-ABS) — Indirect immunofluorescence is entailed to check for treponemal antibodies.9 An FTA-ABS may be useful three to four weeks following initial syphilis exposure, and may be utilized with a blood test to measure treponemal antibodies in someone's CSF and help diagnose neurosyphilis.
  • Treponema Pallidum Particle Agglutination Assay (TP-PA) — A TP-PA checks for treponemal antibodies and is usually performed for confirmation after a previous syphilis test yields positive results. This may be performed instead of FTA-ABS, since a TP-PA tends to be more specific, and there's a lower risk for false positive results.
  • Microhemagglutination Assay (MHA-TP) — According to the American Association for Clinical Chemistry, a MHA-TP assists in confirming the presence of a syphilis infection, but is not utilized as often.
  • Enzyme Immunoassay (EIA) — The EIA checks the blood using antibodies specific to syphilis. "ABC of Sexually Transmitted Infections" notes that EIAs are easier to automate and may produce a positive result during the early stages of the infection.10

The CDC recommends that people who undergo a treponemal test and produce a positive result must take a nontreponemal test with a titer. This aims to fully confirm a syphilis diagnosis, help determine ideal treatment recommendations and see if you need to go through additional testing.

Undergoing a treponemal test followed by a nontreponemal exam means that you're following the "reverse" sequence testing algorithm. While this order can be more convenient for laboratories, there may be problems with its clinical interpretation when it comes to determining whether you actually have syphilis or if you've just been treated for it and have titers for it, even though you've been treated for it.11

Get Over 40% Off on Select Items DailyGet Over 40% Off on Select Items Daily

Who Should Be Tested for Syphilis?

Syphilis testing is a must for people exhibiting symptoms of the infection. Consider having yourself checked for this infection if you:12,13,14

  • Are pregnant and exhibit signs of syphilis (tests must be done during the first prenatal visit, the third trimester or delivery if the woman is at high risk)
  • Are diagnosed with HIV
  • Are a sexually active man with male sex partners (MSM)
  • Are taking pre-exposure prophylaxis (PrEP)15 to prevent HIV
  • Had sexual intercourse with someone recently diagnosed with syphilis
  • Were previously infected with STDs16 or are currently diagnosed with other STDs
  • Are engaging in high-risk sexual activity, such as having unprotected sex with multiple partners

You can also ask your doctor if you can undergo syphilis testing even if you don't exhibit symptoms or if you're unsure if a partner has been infected. If you're sexually active, you should talk about your risk for the infection with your doctor and ask if testing for syphilis or other STDs is needed.17

Testing Guidelines for Pregnant Women

As mentioned earlier, pregnant women are highly recommended to be screened for syphilis. This is because an untreated syphilis infection can be passed from mother to child and result in complications. The CDC notes that babies whose mothers tested positive for the disease during their pregnancy must be checked for congenital syphilis.

A quantitative nontreponemal test performed on infant serum may be recommended by your doctor. If the result is reactive, symptoms of congenital syphilis must be examined.

Checking of body fluids, tissues like the umbilical cord or placenta or suspicious sores is possible too by using darkfield microscopy, PCR testing or special stains. In some cases, the doctor may also want to analyze the baby's CSF by using VDRL, or recommend other tests like cell count and protein, CBC with differential and platelet count and long-bone radiographs.18


Syphilis: Introduction

What Is Syphilis?

Tuskegee Syphilis Study

Congenital Syphilis

Syphilis Stages

Syphilis Causes

Syphilis Transmission

Syphilis Symptoms

Syphilis Treatment

Syphilis Testing

Syphilis Prevention

Syphilis FAQ

< Previous

Syphilis Treatment

Next >

Syphilis Prevention

Click Here and be the first to comment on this article
Post your comment