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Avatar universal

Flu shot and HIV antibody test

Two questions:

1) Is a HIV antibody test at 16 weeks (negative) conclusive, or do you have to wait to the 6 month mark?  Also, in the forum, you seem to always say that results are really reliable earlier than 3 months unless there has been significant exposure... I don't understand why the type of exposure would have anything to do with the testing timelines.  Can you help me understand?

2) I had a flu shot last Thursday, and on Friday I did a Home Access test for HIV antibodies.  I will get the results tonight (it's now 18 weeks since I got someone's HIV+ semen on my knee while masturbating together).  Can a flu shot affect (false positive) a HIV antibody test?  I know that Home Access doesn't do the Western Blot, but uses elisa and then a different confirmatory test.  I have read that flu shots can cause false positives online, but the sources don't seem to be as knowledgable as the experts here.

Thanks for your time and your reply.  It's great to have a source where you can go to on the internet that is professional, expert-driven, and helpful.  I appreciate you two!
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239123 tn?1267647614
MEDICAL PROFESSIONAL
Welcome to the forum.  Directly to your questions.

1)  With the routine HIV antibody tests in standard use, it never takes longer than 3 months, (and probably never longer than 6-8 weeks) for positive results in newly infected people.  Six months is an urban myth, left over from older tests not in use for over 15 years.

The interaction between risk level and test interpretation has been described several times on this forum.  Here it is again.  Imagine an exposure that carried a 1% risk of catching HIV, and a test that is 90% accurate, such as an antibody-only test at 4 weeks.  A negative test result at 4 weeks means the chance the person actually has HIV is 0.01 x 0.1 = 0.001, or 1 in 1,000.  A definite improvement in odds, but obviously not high enough to be completely reassuring.  Now consider an exposure that carries only 1 chance in 10,000 of transmitting HIV, e.g. oral sex on an infected man.  A 90% reliable test reduces the chance the person was infected to 1 chance in 100,000.  Same test, but a 100-fold more reliable result.  And in many circumstances on this forum, the pre-test probability of HIV is as low as 1 in a million.  Such persons really don't need testing at all, but if they do it and a 90% reliable test is used, they reduce their odds of infetion to 1 in 10 million, which is zero for all practical purposes.

For these reasons, when people are concerned about an HIV exposure, the strength of our reassurance on this forum takes all relevant information into account -- the nature of the exposure, partner's likely infection status, symptoms, etc -- not just the test result.  The test is only part of the story, and often a rather small part (which is why we often advise people that no testing is needed at all, when the risk level is low).

2) There are no health conditions, drugs, or treatments that materially affect HIV seroconversion time.  Profound immunodeficiency mgith do it, e.g. potent chemotherapy or terminal illness -- but even there are theoretical only, with few if any actual reported cases of altered HIV antibdoy test results.  Certainly influenza or other immunizations have no effect.  Western blot is not done when the ELISA test is negative; it's only purpose is to confirm a positive, not to investigate possible false screening tests.

Bottom line:  No matter what sort of HIV risk you had, your negative antibody test is 100% reliable.  And anyway, the non-exposure event you describe carried no risk at all -- so you're also one of those who didn't need testing anyway.  If your blood test had been positive, it would have been necessary to explore other possible exposure you didn't know or were being untruthful about.  No responsible health authority or other expert would accept semen on skin as a source of HIV.

So you can move on with 100% assurance you don't have HIV.

Regards--  HHH, MD
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Avatar universal
Thank you... I appreciate your expertise and opinion.   I have only one further question... after months of on and off diareah, I just tested positive for cdiff.  The pharmacist, knowing that I don't take antibiotics and at age 50 haven't been in a hospital or home, said "that usually only happens to someone with a compromised immune system."  Does that change your opinion.  I'm scared .. just fyi, I did have a dnahiv test too (neg at 7 weeks)
Helpful - 0
239123 tn?1267647614
MEDICAL PROFESSIONAL
Immune deficiency (of the type caused by HIV) is not a common predisposing factor for C. dificile.  Like many infections that started out as primarily hospital based -- e.g. methicillin resistant Staph aureus (MRSA) -- C dif is increasingly common in non-hospitalized patients.  Follow-up with your doctor about the intestinal infection, but stop worrying about HIV.  It simply is not an issue for you.
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Avatar universal
I have been traveling, but read your replies before I left.  I know you get a million questions, so I hope this one post doesn't clutter your inbox more than it already is.  I just wanted to say "thanks!"

I am on day 4 of Flagyl for the C-diff -- I really don't know how I contracted it, or why it took my sytem down so hard with the diareah starting shortly after my low/no risk exposure 4 months ago -- probably just coincidence.  Also got diagnosed with low-testosterone (I'm 50), and that is a bit early too.  

No reply needed -- unless you feel like typing -- just wanted to say "thanks again" for a great service and your incredible helpfulness.  If I need more advice (HIV/STDs), I hope you don't mind me coming here to ask.  I still don't know how you get to all these questions, and how much time you must add to your day to write such detailed/specific replies.
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239123 tn?1267647614
MEDICAL PROFESSIONAL
Thanks for the thanks.
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Avatar universal
I almost feel sorry to ask one more question, but I promise that -- as you often say -- "this will end this thread" after your reply as I don't want to go down the path of anxiety-ridden stupidity.  But, here's the whole story:

I'll cut to the chase, so you don't have to read a lot:

1) Two instances of masturbation with other men.  Both were promiscuous guys and both were admittedly bottoms.  The first reached over and tried to masturbate me in a steamroom (I stopped him, but he may have had preseminal fluid on his hand, and I am NOT circumsized, leaving a large target for HIV).  The second was a male massage therapist who obviously wanted to give more than I bargained for and put his erect penis in my hand, rubbed it there, and then ejaculated getting a few drops of semen on me.  He tried to masturbate me too, but through the sheet covering me.
2) A few weeks after this happened, and after not having slept since the day it happened for more than 3-4 hours a night, I had night sweats, rash in scalp, diarreah, painful muscles, and break-out on face (which being 51 isn't usual, though I do have Rosacea).
3) I was diagnosed with low testosterone at 2 months after this happened.   I read that low testosterone may be caused by HIV.
4) I was diagnosed last week with c-diff, since my diareah has continued for the past 3 months (on and off).  I mentioned that I hadn't taken antibiotics, and wasn't in the hospital.  C-diff can be caught in the public now, but it usually doesn't affect anyone unless their immune system is weakened.

So much for cut to the chase, but...
1) I had several (7) HIV antibody tests between 2 and 18 weeks (all neg).
2) I had a HIV DNA test at 7 weeks (neg).

I've read that some people take up to 6 months -- you say that's an urban myth, but I just need one last reassurance.   With all of this going on, is it possible it could be HIV, or does it have to be something else?  I want to get back into the swing of things sexually at home, but am afraid since I haven't felt well since May.

Again -- last question -- last answer -- this will END this thread and, unless something turns up positive, I won't bother you again.  I really do appreciate your help and expertise.  I'm just going through something odd, and I need your advice on last time.
Helpful - 0
239123 tn?1267647614
MEDICAL PROFESSIONAL
This additional information doesn't change my opinion or advice.  You had exposures that could not have resulted in HIV transmission even if a partner had the virus; andyour test results prove you were not infected.  You should indeed "get back into the swing of things sexually at home", indeed should have done so a long time ago.  Your fears of HIV are truly irrational and I believe professional counseling will help; additional HIV testing will not.  I suggest it from compassion, not criticism.

Experience teaches that allowing anxiety-driven threads like this to continue simply inflames the anxiety, and this is not a substitute for professional care.  If you continue this thread, the entire thread will be immediately deleted.  And please do not be tempted to start a new thread that repeats the same issues/questions.  Call it tough love, but that's the way it is.
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Avatar universal
Sorry, and thanks.  I will seek counselling, and your comment was not taken as a criticism.  Indeed, you seem like a truly compassionate individual.
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