Interpreting syphilis test results is more complex with syphilis than with other sexually transmitted infections. A positive syphilis test can mean several things, including newly contracted syphilis or previously treated syphilis.
- RPR and VDRL are nontreponemal tests, meaning they are not specific for syphilis
- FTA-ABS, TPPA, EIA, and CLIA are all treponemal tests, meaning tests specific to the syphilis bacterium, Treponema pallidum
EIA, CLIA |
RPR |
VDRL |
FTA-ABS |
TPPA |
Syphilis Test Interpretation |
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This pattern of syphilis test results can mean any of these three things:
If testing was for diagnosis and the patient has no history of syphilis
The results are positive for syphilis.
If
testing was for diagnosis and the patient has a history of syphilis
The results are considered positive if the titer (number) in nontreponemal test (RPR) results is four times higher than the previous
test titer.
If testing was after syphilis treatment
When a follow-up test is positive, the patient’s health care provider should review the previous results and the report, especially changes in the
RPR titer. |
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This pattern of syphilis test results can mean any of these three things:
If testing was for diagnosis and the patient has no history of syphilis
The results are positive for syphilis.
If testing was for diagnosis and the patient has a history of syphilis
The
results are considered positive if the titer (number) in nontreponemal test (VDRL) results is four times higher than the previous test titer.
If testing was after syphilis treatment
When
a follow-up test is positive, the patient’s health care provider should review the previous results, especially changes in the VDRL titer. |
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This pattern of syphilis test results can mean either of two things:
For low-risk people (most people)
The results are interpreted as negative—that is, there is no evidence of infection. For high-risk people (homosexual males, people having unprotected sex or sex with multiple sexual partners, etc.)
A
retest should be done. |
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This pattern of syphilis test results can mean any of these three things:
For people with no history of syphilis
The patient probably has syphilis (e.g., early or latent).
For people with a history of syphilis
The
results merely reflect that the person has had syphilis that’s been treated. |
Positive nontreponemal test with positive treponemal test
A positive nontreponemal test (RPR or VDRL) combined with positive treponemal tests (FTA-ABS and TPPA) means, of course, that the overall syphilis testing is positive. This does not necessarily mean that the person tested has
syphilis.
Whether the person has a history of syphilis is important and must be considered along with the test results.
No history of syphilis
The results are interpreted as the patient now having syphilis.
A history of syphilis that has been treated
- If the titer (number) on the nontreponemal test (RPR) is negative, the results are interpreted as negative.
- If the RPR titer number stays low positive after treatment (which is referred to as being in a serofast state), the results are considered negative.
- If the titer (number) on the nontreponemal test is four times higher than the post-treatment number, the results are considered positive.
Positive nontreponemal test with negative treponemal
A positive nontreponemal test (RPR and VDRL) combined with a negative treponemal (confirmatory) test (FTA-ABS or TPPA) means that the nontreponemal result was a false positive (since the positive result wasn’t confirmed by
the treponemal test).
About 1% to 2% of people tested for syphilis in the United States have false-positive results. (Importantly, false-positive results have a low RPR titer (number).
False-positive syphilis test results are most common in certain patients: those who are pregnant; those who have lupus, HIV, or endocarditis; and those who have recently been immunized.
If retested in about six months, a syphilis test that had been a false positive is usually back to normal (i.e., negative).
Positive treponemal test with negative nontreponemal test
A positive treponemal test (FTA-ABS or TPPA) combined with a negative nontreponemal test (RPR and VDRL) can indicate either of two things:
- The patient has had syphilis in the past that was successfully treated (the past treatment must be verified or at least recalled by the patient).
- The patient may have syphilis now and further testing is necessary to make this determination.