[Question #12357] Regarding testing accuracy

8 months ago

Hi Dr, im 27M , past 6 months ive had a few exposure with FSW. I had exposure on the 6/7 , 10/7, 18/7 and 28/8 all vaginal protected, unprotected fellatio and cunnilingus . Then I got tested for syphilis(rpr), hiv (4th gen) , gono, chlamydia and herpes on the 5/9 ( 9,8,7 weeks and 9 days post exposure) all negative. As I read from the web that most testing is conclusive by 6 weeks. Then for my 28/8 exposure, since HIV is very low risk, my concern is syphilis which I got tested with home finger prick syphilis rapid test kit which had 99.92 sensitivity and 99.97 specificaty on the 2,4,6,8,10 and 11 weeks post exposure . 15 weeks after exposure i didnt have any syphilis symptom on my penis or rashes on my hand and feet just notice a bare spot on my tongue which become smaller and again bigger during this 3 months which I think it was glossitis or geographic tongue. If its help, I live in a Country with 30 mil population, 90% of hiv cases is from male , new cases of syphilis on 2022 is 4700 (the only data i can get) My Question is :

1. Can I consider all my test is conclusive for the 28/8 exposure ? Given that I only use finger prick syphilis rapid test kit?

2. Is the finger prick syphilis rapid test accurate and reliable? Most ngo and free clinic use this test cassette to do screening

3. Does is possible for primary or secondary syphilis to show after 15 weeks ? Im quite confused with the timing of primary and secondary syphilis.

4. What is the risk of getting syphilis from cunnilingus, if she unaware that she has syphilis? Is it common ?

Thank you

H. Hunter Handsfield, MD

8 months ago

Welcome to the forum. Thank you for your confidence in our services.

First, you describe very safe sexual exposures, even if one or more of your FSW partners was infected with HIV, syphilis, or other STI. It is unlikely you were infected. Second, absence of symptoms (urethral discharge, painful urination, penile sores) are strong indications you were not infected. Third, all the tests you mention are highly accurate: you can rely on the negative results you have had. You have been seriously over-tested!

Those comments largely answer your specific questions, but to be explicit about each of them:

1,2. The rapid finger stick tests for syphilis are very accurate and confirm you were not infected. Any result more than 6 weeks after exposure is 100% conclusive.

3. Primary syphilis (chancre, i.e. syphilitic ulcer) usually appears 2-4 weeks after exposure and always within 6 weeks. Secondary syphilis can start anywhere from 6 weeks to 12 months after exposure, but usually begins after 2-3 months. Your negative test results show you were not infected.

4. Cunnilingus can risk syphilis if the female partner is infected, but is rare; and syphilis is rare in FSWs in most countries. But anyway, the risk of syphilis or other STDs at the time of your exposures no longer matter at all, because the test results (and your lack of symptoms) show you were not infected.

I hope these replies are reassuring. Let me know if anything isn't clear.

HHH, MD

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8 months ago

Thanks for the reply Dr, its good to here it straight from experts like you. I agree with you that i'm way overtested and i dont have syphilis.

For my follow up question:

1. Is there any difference in terms of conclusviness and accuracy in different method of testing? Lab testing like rpr,vdrl(blood from vein) or self test (finger prick). For my case im using rapid POC test that give out results in 20 minutes, i believe that this POC test is treponemal, is it correct?
2. If someone with syphilis chancre and it heals own its own but still untreated, can he/she transmit to other partner? Maybe tear from sex itself? I read from your forum you said that no sore no transmission.

3.I read from most webs agreed that syphilis is uncommon in heterosexual and my doc friend also said that cunnilingus is the least way of std transmission, is it true?

Thank you

H. Hunter Handsfield, MD

8 months ago

1. Yes, the POC test is a treponemal test. All syphilis blood tests, both POC and lab based, and both treponemal and non-treponema (like RPR) are conclusive by 6 weeks after exposure. In addition, absence of an obvious sore (chancre) at the site of exposure -- your mouth and lips -- is additional evidence you weren't infected.

2. Yes. Syphilis is highly transmissible during the first few months after catching it, with or without visible chancres or other skin lesions.

3. Both those statements are true.

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8 months ago

Thanks for answering Dr, for my last follow-up questions

1. Is there any difference in testing accuracy when different sample is used(whole blood, serum,plasma)?

2.I read that doxycycline is the second choice treatment for syphilis, I currently taken syphilis for the past 21 days (100mg x 2 a day) for one months , for severe acne which I have for the past year, if i unknowingly have syphilis ( which Im not) , does it effectively cure syphilis?
3. How effective is doxy if taken 72 hours after suspected high risk sexual activity (i.e anal sex) ?

4. As a heterosexual individuals who consistenly use condom, what other std im at risk from oral sex other than syphilis? what is the numerical estimation to get infected from mentioned stds?

Thank you

H. Hunter Handsfield, MD

8 months ago

1. The syphilis blood tests are equivalent for all those samples.

2. That dose of doxycycline is 100% effective prevention syphilis if exposed, and also would cure syphilis less than a year in duration. (If present more than a year, 4 weeks of doxycycline is recommended.)

3. Nearly 100% effective in preventing syphilis.

4. The main other STDs of importance from oral sex are gonorrhea, nongonococcal urethritis (probably due mostly to oral bacteria) and herpes due to HSV1. The risks for all these usually are low, but it depends on the nature of the partner and other details. And condom use, of course.

That completes the two follow-up comments and responses included with each question and so ends this thread. I hope the discussion has been helpful. My overall advice remains the same: you had safe sexual exposures and are unlikely to have any STD as a result. Move on with no further worry. Best wishes and stay safe.

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