Can Long-Term Syphilis Infections Go Undetected in Blood Tests?

Late-stage syphilis follow-up?

I would like to ask the doctor if it is possible that after being infected with syphilis and not getting tested for over ten or even twenty years, the PRP or VDRL tests might yield a negative result? I engaged in risky behavior around the age of 18, and it wasn't until I was 26 during a military physical examination that I was tested for syphilis (which was negative at that time).
When I was 30, I went to a health center for a blood test, and that result was also negative.
Therefore, I would like to know if it is possible that between the ages of 18 and 30, I could have been infected with syphilis but the tests did not detect it.
The method used at National Taiwan University Hospital was RPR/VDRL, and I assume it was one of those two.
The health center sent the sample to the health bureau using RPR.
I am concerned that due to the long duration, the RPR testing method might not detect syphilis.

The doctor's response is: All tests can have errors.
Syphilis testing is done through serum, and some individuals may have a weaker response, leading to misinterpretation.
It is advisable to go to a larger hospital or a more reputable testing facility for more accurate results.
If you have concerns, you can visit a nearby medical institution for testing.
However, I am worried that due to the long time elapsed, it may not be detectable.
I have already undergone RPR testing for syphilis at "National Taiwan University" during my military examination at age 26, and again at the "Health Bureau" when I was 30, and also at a designated hospital for HIV at the same time.
So, I have had three tests done, and these three institutions should have very high credibility.
I engaged in risky behavior at age 18 and had three tests between the ages of 26 and 30.
Should I continue to get tested for syphilis? Should I be concerned that it might not be detectable?

Niming, 30~39 year old female. Ask Date: 2015/08/10

Dr. Xu Weikai reply Urology

Hello, if you have tested negative multiple times, it is likely that you are not infected.
If you still have concerns, various medical institutions in different counties and cities offer free anonymous STD screenings, which you can inquire about.
If you have any doubts, you can visit a nearby medical facility for relevant testing.
If there are any unclear points, feel free to ask again for further discussion.
Online responses should only be used as a reference; if necessary, you should seek medical attention at a healthcare facility.
The Ministry of Health and Welfare, Taitung Hospital, cares about you.

Reply Date: 2015/08/10

More Info

Long-term syphilis infections can indeed go undetected in blood tests, particularly if the infection is in its late stages or if the individual has developed a low-level immune response. Syphilis is primarily diagnosed through serological tests that detect antibodies in the blood, such as the Rapid Plasma Reagin (RPR) and the Venereal Disease Research Laboratory (VDRL) tests. These tests measure the presence of non-specific antibodies that are produced in response to the infection. However, there are several factors that can lead to false-negative results, especially in long-term cases.

Firstly, it is important to understand that the immune response to syphilis can vary significantly among individuals. Some people may not produce detectable levels of antibodies, especially in the later stages of the disease. In fact, studies have shown that in late syphilis, the RPR and VDRL tests may yield low titers or even negative results. This phenomenon is particularly pronounced in cases of neurosyphilis, where the serological response may be diminished.

Moreover, the timing of the tests is crucial. Antibodies typically take time to develop after infection. In the case of syphilis, antibodies can take several weeks to months to become detectable. If an individual was infected but tested too early, the test may return a false-negative result. Additionally, if a person has been infected for a long time without treatment, the body's immune response may weaken, leading to undetectable levels of antibodies.

In your case, you mentioned that you had potential exposure to syphilis at age 18 and underwent testing at ages 26 and 30, both of which returned negative results. Given that you have been tested multiple times at reputable institutions, it is reasonable to conclude that you are unlikely to have an active syphilis infection. However, the concern about long-term infections going undetected is valid, especially considering the nuances of serological testing.

If you are still worried about the possibility of a past infection, it may be beneficial to consult with a healthcare provider about further testing options. More specific tests, such as treponemal tests (e.g., FTA-ABS), can confirm the presence of antibodies specific to Treponema pallidum, the bacterium that causes syphilis. These tests are generally more reliable in detecting past infections, even if the RPR or VDRL tests are negative.

In summary, while it is possible for long-term syphilis infections to go undetected, your history of multiple negative tests at reputable facilities significantly reduces the likelihood of an undiagnosed infection. If you have ongoing concerns, discussing them with a healthcare professional and considering additional testing may provide further peace of mind.

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