Explanation

TPHA (syphilis): what is measured?

TPHA (Treponema pallidum hemagglutination assay) detects antibodies aimed specifically at Treponema pallidum, the bacterium that causes syphilis. It is a so-called treponemal test. These antibodies usually remain detectable for life, even after proper treatment. The TPHA therefore tells whether you have ever had syphilis, but not whether the infection is active now. With a positive result, the laboratory also reports the TPHA titer: a measure of the amount of antibodies. This titer does not reliably tell whether the infection is active either; that requires a different test, the RPR.

What can it detect?

Syphilis in the first or second stage, from a few weeks after infection
Latent syphilis: an infection without symptoms that can last for years
A syphilis you have had and been treated for in the past

Result

What does the result mean?

Positive result

A positive TPHA means that antibodies against the syphilis bacterium have been found. This fits an active syphilis, but also a syphilis that has already been treated, because the antibodies usually do not disappear. The TPHA titer shown with the result can remain high even after successful treatment and therefore does not tell whether you have an active infection now. According to the LCI guideline (RIVM), a confirmation test (IgG western blot) and an RPR test follow to determine whether the infection is active. Sometimes the test reacts to antibodies against related bacteria that cause skin infections in tropical areas (such as yaws); blood tests cannot distinguish these from syphilis. Without treatment, syphilis does not go away on its own and can damage the brain, eyes, heart and blood vessels after years, but it can be treated well with antibiotics.

Negative result

A negative TPHA means that no antibodies against the syphilis bacterium have been found. In the first weeks after infection, the antibodies are often not yet detectable. If early syphilis is suspected, such as a painless sore after sex, the LCI guideline (RIVM) advises repeating the blood test after 3, 6 and 12 weeks; with such a sore, a test on the wound fluid (PCR) is the first choice. If antibiotics have already been used, the test can stay negative for longer or even permanently.

After an abnormal result

With a positive result, a confirmation test and an RPR test follow, and the doctor also tests for HIV and other STIs. With an active syphilis, treatment with antibiotics follows and sexual partners are informed, tested and treated if needed. Syphilis is not notifiable for individual cases.

Reliability

How reliable is the test?

The TPHA is one of the standard tests for detecting syphilis. According to the LCI guideline (RIVM), a positive treponemal test is followed by a confirmation test (IgG western blot) and an RPR test for the activity of the infection. Because the antibodies remain for life, the TPHA is not suitable for monitoring the effect of treatment or for detecting a new infection in someone who had syphilis before; the TPHA titer is not suitable for this either. For that, the doctor uses the RPR test.

What can affect the result?

In the first weeks after infection, the test is often still negative; if early syphilis is suspected, a repeat after 3, 6 and 12 weeks is needed.
Using antibiotics shortly after infection can delay or prevent the formation of antibodies.
Cross-reaction with related tropical treponemal infections (yaws, pinta, non-sexually transmitted syphilis) gives a positive result that cannot be distinguished from syphilis.
After treated syphilis, the test usually stays positive and then says nothing about a new infection.

Who it is for

Who is the test useful for?

Useful for

Useful after sex without a condom with a new or changing partner, for men who have sex with men, sex workers and people with HIV, if a partner has syphilis, and with symptoms such as a painless sore on or around the penis, vagina, anus or mouth, or a non-itchy skin rash on the trunk, arms and legs. Pregnant women are already tested as standard in the first trimester. For people who have had syphilis before, the TPHA is not suitable for detecting a new infection.

How common is it?

In 2024, syphilis was diagnosed in 1,798 people at the Sexual Health Centers; 92 percent of them were men who had sex with men. Syphilis is also more common in people with HIV. Almost no babies with syphilis are born in the Netherlands (zero to three per year), because all pregnant women are screened.

The RIVM (Sexual Health Centers, 2024); the LCI guideline on syphilis

Drawbacks and risks

A positive result due to a syphilis treated long ago or a related tropical infection can cause unnecessary worry or confusion about an STI.
Testing shortly after a risk contact can give false reassurance if no retest follows.

Get tested

TPHA (syphilis): test panels

TPHA (syphilis) is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.

Blood draw
Syphilis
Serology for syphilis; screening and confirmation.
€ 32,00
Blood draw
Syphilis including titer determination
Serology including titer; for syphilis diagnostics.
€ 51,00
Multiple samples
Complete STI home test
Test at home for chlamydia, gonorrhoea, trichomonas, Mycoplasma genitalium, HIV and syphilis.
€ 99,00
Multiple samples
Comprehensive STI home test
Our most extensive at-home STI test for twelve infections and pathogens, including HIV, syphilis, hepatitis B and herpes types 1 and 2.
€ 149,00
Fingerstick
HIV, syphilis and hepatitis B home test
Three serological STI screens from one fingerstick sample.
€ 59,00
Fingerstick
Syphilis home test
Laboratory screening for syphilis with confirmation if required.
€ 39,00

Evidence

Sources

This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.

More about risks and results

More explanations

Other tests: STIs

All tests

TPHA (syphilis)

TPHA (syphilis): what is measured?

What can it detect?

What does the result mean?

Positive result

Negative result

After an abnormal result

How reliable is the test?

What can affect the result?

Who is the test useful for?

Useful for

How common is it?

Drawbacks and risks

TPHA (syphilis): test panels

Syphilis

Syphilis including titer determination

Complete STI home test

Comprehensive STI home test

HIV, syphilis and hepatitis B home test

Syphilis home test

Sources

Other tests: STIs

TPHA (syphilis)

TPHA (syphilis): what is measured?

What can it detect?

What does the result mean?

Positive result

Negative result

After an abnormal result

How reliable is the test?

What can affect the result?

Who is the test useful for?

Useful for

How common is it?

Drawbacks and risks

TPHA (syphilis): test panels

Syphilis

Syphilis including titer determination

Complete STI home test

Comprehensive STI home test

HIV, syphilis and hepatitis B home test

Syphilis home test

Sources

Other tests: STIs