How Accurate Is The Rapid Anti-body Test For Syphilis?

Posted on Mon, 25 Aug 2014

Question: Hi Doctor, My wife (32 years old, second pregnancy, no history of miscarriage) is 17 weeks pregnant and we got her VDRL test results back which showed a positive result of 1:2. Her Doctor has recommended her to do a VDRL retest (as test was done 4 weeks ago).
Meantime while waiting for the test result I have gone ahead and done a Syphilis Rapid Anti-Body Test and test result came out negative. The GP who performed the test said the test is 99% accurate and is unlikely to show a false negative.
I would like to enquire:
1. How accurate is the Rapid Anti-Body Test. Do I need to get myself tested again just to be sure?
2. If my wife's second VDRL test comes back positive, would it be recommended to start treatment on mother and baby?
3. What is the percentage of false positives in pregnant women?
4. Is it necessary for my daughter (4 years old) to get tested as well?

Answered by Dr. Shanti Vennam (2 hours later)

Brief Answer:
Detailed below.

Detailed Answer:
Hello,

Thanks for writing to us.

Here are your answers--

---The rapid antibody test is sensitive but not specific, i.e., it can give false positive results as it can also read non-treponemal infections. As you have a negative result, you need not be tested again.

---If the second test for VDRL is reported positive, treponemal antibody tests are recommended to come to a conclusion on the diagnosis. Treatment may be initiated after proper diagnosis.

--the percentage of false positives in pregnancy is about 0.7 percent

--if congenital or early neonatal infection is suspected, your daughter may also need to be tested to plan further management.

Hope your queries have been answered. Please feel free to contact for further clarifications. I will be happy to help.

regards,
Shanti.V.

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Shanti Vennam (16 hours later)

Hi Dr,

We received my wife's retest results and VDRL is 1:2 (unchanged) and TPHA test was reactive.
I went ahead and also did a VDRL and TPHA test both of which came back non-reactive.

I do not believe my wife has had Syphilis before hence I am abit puzzled by this result and would like to seek your professional opinion. Assuming my wife has never contracted Syphilis before, does this mean that she has contracted syphilis? If so, why is my test result negative considering that we have been having sexual intercourse.

Answered by Dr. Shanti Vennam (2 hours later)

Brief Answer:
False positive test is possible in pregnancy.

Detailed Answer:
Hello,

Thanks for writing again.

Treponemal tests give positive result one to two weeks after exposure and not earlier. False positive results are seen during pregnancy, some viral infections, autoimmune diseases, skin diseases etc.

Considering the fact that there has been no chance of exposure, though rarely infection can occur through close bodily contact and not necessarily through intercourse, it appears that it could be a false alarm. Please take a second opinion from a specialist in person.

Hope I have clarified your query. Please contact for any more information. I will be ready to help.

regards,
Shanti.V.

Note: For more detailed guidance, please consult an Internal Medicine Specialist, with your latest reports. Click here..

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar