[Question #5163] Awaiting TPPA Result

25 months ago
I had a brief heterosexual encounter with a CSW in Texas on February 3. Deep kissing and then very brief oral sex (receiving) perhaps 10-15 seconds at the most. Almost exactly 5 weeks later (March 10) I noticed a small ulceration on my foreskin about halfway down my penis, painless, not dry but not particularly wet either - more like a healing wound. It was forming a light scab. Two days later I went to get tested. Came back negative for everything, including RPR test for syphilis, which was nonreactive. I requested a TPPA test on the same blood and it also came back negative. 

A week later the ulcer had cleared up and you could just barely see where it had been. I felt sporadic pains in my thigh/groin area during that week. On March 20 (6.5 weeks after the encounter) I went to the local STI clinic. RPR and "Syphilis Health Check" both nonreactive. They sent a blood sample to the state lab for TPPA test. I am expecting that result any day now. The ulcer was no longer visible for the APRN to examine, but she performed a physical evaluation, including checking my groin for other signs of infection and for swollen lymph nodes etc. Said she didn't find anything suspicious.

Questions:
(1) How reliable are the blood test results that I've had so far? What would you expect the TPPA result to be?
(2) Can you speak generally to the accuracy of these types of blood tests (RPR, SHC, TPPA) for someone who is possibly symptomatic for syphilis? Is it possible to have the chancre come and go without a test at the beginning and end of that process being positive?
(3) Is it possible that having a chancre appear at 5 weeks (instead of the "average" of 3) indicates a delayed syphilis process, including production of antibodies, which then causes the tests to be negative beyond the 6 week window?

Thank you in advance for you response. You all do great and informative work.
Edward W. Hook M.D.
Edward W. Hook M.D.
25 months ago
Welcome to our Forum.  I'll do my best to help.  The exposure you describe was very low risk- syphilis is a relatively rare diseases and while it has increased in the U.S. in recent years, 70-80% of infections are occurring among men with other men as sex partners.  Syphilis is women, even CSWs is uncommon.  further, when people (including CSWs) have syphilis, oral lesions are very rare.  Finally, most people who acquire syphilis will develop a positive blood test by 30 days after exposure despite the "conventional wisdom" that the disease can incubate for as long as three months.  Putting all of these facts together and considering your repeatedly negative tests, you are more likely to be struck by lightening that to acquire syphilis from the exposure you describe.  Thus:

1. Very reliable.  Your TPPA will be negative as well
2.  These tests are highly reliable and particularly when two different types of tests are done.  
3.  "possible" I suppose, if you had taken antibiotics in the interim.  Otherwise, please refer to my statement regarding your risk of being struck by lightening above.

If I were you, I would not be the least bit worried and would be moving forward without continuing concerns.  EWH
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25 months ago
Dr. Hook, thank you for your response. Sincerely appreciated! I have a couple of follow-ups (mostly out of intellectual curiosity, but also because people are sometimes struck by lightning...)
(1) Can you explain the relationship between the appearance of a syphilis chancre and when the disease is detectable by blood tests? i.e. would you definitely test positive when the chancre first appears, or when it is gone? Or are these events unrelated and the only significant metric is time from the initial exposure? In my case the ulcer/chancre lasted only ten days (starting at day 34) so once it is gone would I for sure test positive on RPR/TPPA?
(2) The common WHO graph here (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4999316/) seems to indicate that only 90% of people with syphilis will test positive on RPR at any point, and that during primary syphilis that rate is much lower (40% even when chancre is present). Do you know what explains the gap between what this chart shows and the guidance that you and Dr. Handsfield provide?
(3) The Texas state lab that's doing my second TPPA test states: "At the time of appearance of the chancre, only about 25% of the cases will have a reactive RPR test. After the chancre has been present for one week, 50% will have a reactive test; after two weeks, the ratio rises to 75%. Almost all will have reactive serologies 3-4 weeks after appearance of the primary lesion."
Are they just misinformed somehow? Per that advice it seems I could well test positive in a week or so for the first time.

Thank you for considering these questions. I know I and others sincerely appreciate your advice and help. You and Dr. Handsfield have the patience of saints!
Edward W. Hook M.D.
Edward W. Hook M.D.
25 months ago
1.  Typically syphilis blood tests, and in particular the TPPA are positive within 2-3 days of appearance of a lesion.
2.  WHO data are, unfortunately, conservative and reflect the "problem laboratories" in many lower and middle income nations.
3.  The Texas lab statement is overly conservative, something that, to be honest, is in their interest (no governmental agency is willing to ever be "wrong", even when they are, hence they err on the conservative side of things.  EWH
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25 months ago
Thank you again for your response. I know I have just once reply left. I want to ask your opinion on my physical symptoms and a couple of other items.

I know I have had negative blood tests at 5 weeks and 6.5 weeks, the first at the time of appearance of a penile ulcer and the second as it was basically gone, but the fact that I had this symptom (together with some sporadic pains in my groin/thigh area) remains concerning to me.
(1) What, if not syphilis, could have caused both of these symptoms simultaneously? I have never had anything like this before and the encounter I had was the only sexual activity within a couple of months of the symptoms developing. It seems like an almighty coincidence to me, in spite of the blood tests.

Other questions:
(2) Is oral to penis transmission of syphilis predicated on the presence of an oral chancre, or can it occur at other times simply based on the contact between the foreskin and the mucous membrane in the mouth of someone who has syphilis at one stage or another?
(3) Generally speaking, is syphilis transmissible before the appearance of the initial chancre in any way at all (i.e. penile/oral/vaginal?) I've read conflicting answers on that. If the answer is no, then why is that the case?

Meanwhile, still awaiting the result of the 6.5 week TPPA test. Thank you so much for your answers so far.
Edward W. Hook M.D.
Edward W. Hook M.D.
25 months ago
1.  I cannot say what may have caused your genital lesion, nor your genital discomfort.  Nor can I say that they were related. They may not have been an STI but a coincidental occurrence.  This is not uncommon.   That said, I would urge you to believe your blood tests- they are highly reliable and focusing on the STI possibility might keep you from determining what was going on, should they recur.
2.  Syphilis is transmitted through direct lesion contact.  No lesion, no risk.
3.  See my answer above.  Syphilis can be transmitted by lesion contact before a blood test is positive but a lesion would need to be present

I hope these responses are helpful.  I would be willing to bet a large sum of money that your TPPA will show that you did not acquire syphilis.  

Take care.  As you know, this thread will be closed shortly.  EWH
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25 months ago
Very helpful, thank you. I know I don't have any more questions, but if you inclined to answer I'd be appreciative. You say "no lesion, no risk." What constitutes a legion? A visible chancre, or even just the site of a future chancre while the infection is incubating? I've read that such areas are active with the bacteria, but there are just no outward signs until the chancre actually appears. Your patience much appreciated. No further questions from me on this thread. Thank you for all of your help & advice.
Edward W. Hook M.D.
Edward W. Hook M.D.
25 months ago
A lesion is a VISIBLE lesion.  A bump would suffice.  A open ulcerated ulcer (chancre) need not be present.  If a lesion is present the infection is no longer incubating.  EWH---