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Does Septra Interfere With Common STD Tests?

Posted on Tue, 14 Feb 2017

Question: I went to the doctor for a uti and was prescribed septra. I went in for STD test the next morning (18 hours after taking first does). All my results came back negative. Are these results reliable? How long would the antibiotics need to be in my system to create a possible false negative?

Answered by Dr. Sankaranantham Murugan (2 hours later)

Brief Answer:
Septran would not interfere with common STD tests.

Detailed Answer:
Hi,
Welcome to HCM.
Thanks for posting your query.
Different antibiotics have different time to get excreted from our body. Tablet Septran would not interfere with the major and common STD tests for Syphilis, HIV and other viral STDs.
So your results are reliable only provided they would have been done after the window period of each diseases. How long after the exposure you had your tests?
Dr S.Murugan

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

Follow up: Dr. Sankaranantham Murugan (28 minutes later)

I would have been exposed 6 months prior. I was more concerned that my uti could have actually been chlymedia. No reason other than I learned that it can be asymtomactic and started to panic. I felt better after I got my results back, but then I realized I had started antibiotics the day before so I didn't know if that could have caused a false negative. It was only in my system 18 hours, and I read that Septra is not a good treatment for it anyway. But I could not find any conclusive information on how long it would take to suppress the results to a false negative.

Answered by Dr. Sankaranantham Murugan (1 hour later)

Brief Answer:
Possibility of Septran can interfere with the results of Chlamydia.

Detailed Answer:
Hi,
Welcome back.
If your exposure is 6 months prior, then your test reports are highly reliable.
Septran would remain in the body not more than 24 hours. But the intake (course) of Septran would likely be to interfere with the results of Chlamydial tests.
Dr S Murugan

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

Follow up: Dr. Sankaranantham Murugan (41 minutes later)

So to clarify...even though the anti biotics were in my system less than 18 hours it could have caused a false negative result and I could in fact have it and should get retested? Is it highly likely that it gave a false negative or just slightly likely?
Thank you for you time on this. I was hoping to ease the resurgence of anixiy regarding this but now I think I'm just going to have to go through the stress of the testing/waiting process all over again.

Answered by Dr. Sankaranantham Murugan (1 hour later)

Brief Answer:
Depends on what type of test had been used for you.

Detailed Answer:
Hi,
Welcome back.
It depends on what type of test had been used to test. If it is PCR test (detect Antigens), it will not get affected by the antimicrobial whereas if antibody detection test were used, then there was every possibility to have false negative test.
It has to be decided by your physician whether you need further test or not.
Dr S Murugan

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