[Question #11869] STI window test period
11 months ago
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I had unprotected vaginal sex 4 times with a man. He told me he had recently tested negative but he also had sex recently with a Venezuelan migrant to USA. So I’m also concerned his test was too soon after that to pick up STIs.
I took a test yesterday, which was about 19.5 days after the last unprotected sex. Can you tell me how conclusive the test will be at this time and what my follow up should be to completely ease my mind? I am thinking about getting a HIV RNA test sometime too. Could you tell me when that would be conclusive? Here is some more context that I received about the HIV test from a nurse practitioner from one medical:
An HIV screening cascade has been ordered.
it looks for HIV-1 p24 antigen and/or HIV-1/HIV-2 antibodies. A reactive result is considered preliminary and requires additional testing to confirm an HIV infection. If the Ag test is positive but the Ab test is negative, a reflex RNA test will confirm or negate the test.
tests: HIV ab/ag screening cascade, RPR, HBcAb, HCV
My primary care physician said I should feel confident about being negative if these results come in negative but that I could get tested after 6 weeks of potential exposure too. What do you think about how conclusive this test will be? Is there a time sooner I can get tested for conclusive results than 6 weeks for each STI?
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Edward W. Hook M.D.
11 months ago
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Welcome to the Forum. Thanks for your questions. I'll be glad to comment. The time to conclusive results varies between HIV tests. You're nearly 20 day routine HIV test is early and might detect about half of recent infections. For routine, combination HIV p24 antigen/antibody (4th generation) tests, results are about 98=99% conclusive at 4 weeks (28 days) and entirely conclusive at 6 weeks . HIV RNA PCR tests become reliably positive sooner- as soon as more than 11 days after acquistion of infection. Some experts suggest following HIV RNA PCR tests with routine 4th generation tests at 6 weeks but results of the PCR more than 11 days after an exposure are very, very reliable and can be considered virtually conclusive- I would not feel the need to repeat them.
Blood tests for syphilis also take 6 weeks to be entirely conclusive.
Vaginal swab or urine tests for gonorrhea, chlamydia and trichomonas are reliable and conclusive any time more than 3-5 days after an exposure. A self obtained vaginal swab is the preferred test.
I would consider the exposures you describe relatively low risk. Most people do not have STIs and even fewer have HIV. Further most single exposures do not lead to infection
I hope this information is helpful. EWH
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11 months ago
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Thank you Dr. Hook. That is helpful.
Can you tell me when blood test results for hepatitis b and c would be conclusive?
My antigen/antibody tests did come back negative. I am still concerned about HIV and might get a RNA PCR test to ease my worries.
Even though the exposure was low risk, does my risk increase since I had unprotected sex with the person 4 times? Is there a way to give me my percentage of risk based on this information and my recent negative test. I do not trust the person’s words because they displayed some troubling behaviors after the last time we had sex. I have experienced hypochondria related to HIV before and am working on it in therapy but am wondering if I have some OCD related to the subject
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Edward W. Hook M.D.
11 months ago
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For all practical purposes, hepatitis C is not a sexually transmitted infection with the exception of occasional transmission amongst men who have sex with men participating in receptive rectal intercourse. Testing for hepatitis B would be conclusive at six weeks although, if you are under 40 it is more likely than not that you received the hepatitis B vaccine, which is highly protective and therefore do not need testing for hepatitis B.
I’ll provide some figures on HIV transmission. For a woman participating in unprotected vaginal sex with an HIV infected man who is not on therapy, her estimated risk of infection is about one infection in 2000 encounters. Numerically after four episodes that risk increases to one and 500. In other words. after four episodes of unprotected vaginal sex, in the unlikely event that your partner had HIV there would be a more than 99% chance that you would not be infected.
Also, FYI, as a heterosexual male, the statistical likelihood of him being HIV infected is less than one percent. It is for these reasons that I classified your encounter as being low risk. EWH
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