Patient education: Syphilis blood test (The Basics)

What is a syphilis blood test? — This is a way to check or "screen" for syphilis.

Syphilis is a sexually transmitted infection. This is an infection that you can catch through sex. Syphilis is caused by bacteria and needs to be treated with antibiotics.

There are 2 blood tests for syphilis. They check for different "antibodies." These are proteins the body makes when a person has the infection. Some of these antibodies can stay in the blood even if a person had syphilis in the past and was treated.

Why might I get a syphilis blood test? — Your doctor might order this test:

●If you have symptoms of syphilis – Syphilis has different stages. After a person first gets the infection, they usually get a painless, red bump in the genital area. Eventually, the bump turns into a small, usually painless sore with a raised edge. Later-stage syphilis can cause other symptoms, such as a widespread rash, fever, and swollen lymph nodes. Sometimes, the infection can move to the brain, ears, or eyes. This can be serious.

●If you might have been exposed to the infection – For example, if you have a sex partner who has been diagnosed with syphilis, you should get tested even if you don't have symptoms. Doctors also recommend that people who are at high risk for syphilis get tested regularly.

●If you are pregnant – It is possible for a pregnant person to give syphilis to their baby. This can be dangerous. Experts recommend screening for all pregnant people.

●To check if treatment worked – If you got antibiotics to treat syphilis, a blood test can show if the medicine worked to cure the infection.

How do I prepare for a syphilis blood test? — For this test, you need to get a "blood draw." Your doctor or nurse will tell you where to go for this.

It might help to wear a short-sleeve shirt to your blood draw appointment. This makes it easier for the person drawing your blood to get to your arm.

What happens during a blood draw? — For the blood draw, a needle is used to take a small amount of blood from your arm (figure 1). Collecting the blood only takes a few minutes. The blood is then tested in a lab.

Tell the person who takes your blood:

●If you take "blood thinner" medicines or if you have a bleeding problem – They will make sure that your bleeding is under control before you leave.

●If you have a latex allergy – Some of the supplies used for blood draws might contain latex.

●If you have a preferred arm to use

Most of the time, getting blood taken does not cause problems. You might have a little soreness or bruising where the needle went in.

What do my results mean? — Your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.

The results of the test can be:

●Positive (also called "reactive") – This might mean that you have syphilis or had it in the past. Your doctor will do another test to confirm the results. That's because it is possible to get a "false-positive" result. This is when the test comes back positive even though you do not actually have the infection.

If you got the test to check if treatment worked, your doctor will check the level of antibody in your blood. They will repeat the test to make sure that the level goes down over time.

●Negative (also called "non-reactive") – This means that the test did not find signs of syphilis. In some cases, a person can still be infected and get a negative test. This is called a "false-negative" result. Depending on your situation, your doctor might repeat the test in a few weeks.

If you do have syphilis, your doctor or nurse will talk to you about treatment. Syphilis is usually treated with an antibiotic called penicillin.

More on this topic

Patient education: Syphilis (The Basics)
Patient education: Sexually transmitted infections (The Basics)