How Do I Get Tested For Syphilis?

Young female medical professional holding a test tube and talking on a telephone
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Question: How do I get tested for syphilis?

Answer: Syphilis tests are usually, but not always, blood tests.

Need to get a syphilis test? Usually, the process is pretty easy. However, how a healthcare provider tests for syphilis depends on what stage of the disease you are in.

If you have something that may be a syphilis sore (chancre), you may get a swab test. For this test, the doctor will swab the region and look at the sample under a dark field microscope.

This allows them to see if any Treponema pallidum are present. T. pallidum are the bacteria that cause syphilis. Doctors may also use direct fluorescent antibody testing to detect T. pallidum in the sample.

There are also several blood tests for syphilis. Unfortunately,  the main blood test is not good at detecting primary syphilis. It may miss as many as 1/3 of these early cases. That is why dark field microscopy is the gold standard for early diagnosis. This is also why many doctors who do not have access to a dark field microscope will presumptively treat sores that look like syphilis. Presumptive treatment means treating because there is a presumption you have the disease. In this case, it means you might be treated even if the blood test for syphilis is negative.

The primary syphilis blood test looks for antibodies to the disease. It does not directly detect the bacteria. Instead, it lets your provider know if you have been infected with syphilis.

However, it is important to know that the antibodies can stay around for years after successful treatment of a syphilis infection. Therefore, a positive blood test doesn't mean you have syphilis again. That's why if you have been previously treated for syphilis, you should tell your provider in advance.

If you change doctors, it's a good idea to get copies of any blood tests for your next doctor.

There are several additional syphilis tests that can be run on blood samples. Used in combination, these tests can improve diagnostic efficacy. Over time, using a microscope to detect syphilis has become less common.

What is the difference between a treponemal test and a non-treponemal test for syphilis?

Non-treponemal tests look for indirect markers of syphilis. These markers are usually present because of syphilis, but they can also occur for other reasons. Treponemal tests are more specific for syphilis infection. They are less likely to turn positive because of another infection.

Usually, individuals are first tested with a non-treponemal test for syphilis. Then infection is confirmed with a treponemal test. This type of confirmatory testing reduces over treatment.

Note: If you are pregnant, you should ask your doctor to perform a blood test for syphilis. Untreated syphilis during pregnancy can be fatal to the developing baby.

Sources:
Dowell et al. (2009) "Dilemmas in the Management of Syphilis: A Survey of Infectious Diseases Experts" Clinical Infectious Diseases. 49 (Nov 15):EPub Ahead of Print (accessed 10/24/09)

Owusu-Edusei K Jr, Koski KA, Ballard RC. The tale of two serologic tests to screen for syphilis--treponemal and nontreponemal: does the order matter? Sex Transm Dis. 2011 May;38(5):448-56. doi: 10.1097/OLQ.0b013e3182036a0f.

Reisner BS, Mann LM, Tholcken CA, Waite RT, Woods GL. Use of the Treponema pallidum-specific captia syphilis IgG assay in conjunction with the rapid plasma reagin to test for syphilis. J Clin Microbiol. 1997 May;35(5):1141-3.

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