I am a straight male, I did a syphilis rpr by Quest 42 days after exposure. Result was non-reactive. I also had another RPR test done 84 days after exposure. Result was also non-reactive. The only symptom I have is a lymph node in my neck and tightness near the node after my  sexual encounter. I have a worry because I did take amoxicillin pot clavulanate due to the lymph node (did not resolve the node). Im not sure at what time I took it. It mightve been before the 6 week test or after the 6 week test. I am worried that it delayed my syphilis rpr test where it wouldve been positive after the 84 days post exposure but I didnt wait long enough so I got a negative test instead. I worry also because it has been almost 2 years since that event and I can still feel that enlarged lymph node and im worried its due to syphilis or some other sti that was missed. Also I think I should mention I was also tested for all other stis hep b, hiv, gon, chlamydia, at those times as well.

Stopping for an initial reply after reading the first three sentences: Unless there is a big surprise in the rest of your question, you definitely did not catch syphilis. Your test results are conclusive.

Now having read the rest:  No change. The test results overrule any and all symptoms. And from your description, there is no reason to suspect syphilis. The antibiotic you took also would have prevented or cured syphilis before the test had a chance to become positive. Contrary to popular belief, antibiotics generally do not make tests falsely negative while the infection persists.

If you still feel you have an enlarged lymph node, see a doctor about it. But a single enlarged node doesn't suggest syphilis anyway, and no other STI either. Something else is the cause. 

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD

Thank you for your response doctor.

1. I have read on the forum that antibiotics cant cause a false negative but I have read from Dr Hook saying that antibiotics can delay test positivity by slowing the growth of syphilis bacteria? he said it was uncommon but possible. Since I dont remember when I took the antibiotics, hypothetically say I took them on the 4th or 5th week, would it delay a positive where my 6 week rpr would go negative? or say I took the antibiotics after the 6 week test on the 7th week could it then turn my 84 day test negative? or is my 84 day rpr conclusive whether the antibiotics slowed the bacteria growth down or not?

2. I do take L-Theanine Supplements and do take a pretty high dose. Can that affect blood test results?

3. Can Marijuana or using Disposable Vapes affect test results?

2,3. There are no supplements, drugs or non-antibiotic medications of any kind that have any effect at all on syphilis blood tests.

In addition, you describe no symptoms that ever suggested syphilis (despite what you think you learned in searching about enlarged lymph nodes). Had you been infected, probably you would have had an obvious chancre (open sore) at a site of direct contact with a sex partner, well before 4-5 weeks. And as a straight male, if you're in the US or other industrialized country, probably there is little chance you were exposed to syphilis. In other words, entirely apart from the antibiotics and your blood test results, the evidence in overwhelming you do not have and never had syphilis.

Your are unreasonably worried about this. Do your best to let it go.

Thank you doctor,

last question. I heard Biotin can affect hiv tests can it affect rpr as well? As I have used a biotin supplement hair oil for hair growth in the past.

sorry didnt mean to hit submit.

Or is the biotin thing overblown and not really a thing to be concerned about even when taking biotin supplements? cause I feel if it was truly a big concern with testing that doctors would ask if I was taking any biotin supplements before being tested.

This is the first question I've ever heard about biotin and RPR or other syphilis tests. Not an issue.

That completes the two follow-up comments included with each question and so ends this thread. I hope the discussion has been helpful. Best wishes and stay safe.