Do the testing Times Differ According to your Exposure

[Troubled246]

Dear Dr

I have some questions about the reliability of testing and when to test, so I have some questions.

1.  I have consistently seen both this forum and the HIV international forum, plus virtually all private hiv clinics in london state the the HIV duo/combo test is reliable post 28 days/4 weeks - so why is this not considered conclusive by the UK and US authorities?  I remember when I was testing myself, I wanted to believe my duo test result, but with people on the community forums consistently pointing to the 12 week rule for conclusivity its difficult to remain rational in anxious times.  Even my GUM clinic said a HIV insti test is valid at 6 weeks, but then gave me a letter saying this result is negative today, but standard UK guidelines say incubation period is still 3 months!

2.  Is the HIV Duo Test reliable reliable regardless how risky your exposure could have been? So for e.g. having unprotected sex with a known HIV positive person. Or would you and other doctors advise to test out to three months for someone who had a riskier exposure?

3. Why are those people exposed to HIV in an occupational setting i.e. needlestick, surgery etc forced to test out to 12 months to confirm their HIV status, could a HIV duo test not confirm their status at the same time as others outside of the occupational setting.

I guess what I am saying is that whether you are exposed to HIV through drug use, sexual behaviour or an occupational hazzard, should be neither here or there.  Especially when according to the common information form all experts on this forum and medical scientific data seems to point to the fact that most people will develop antibodies by 6 weeks, and even if they don't the duo test will in any case pick up the p24 antigen. So a 4 week duo should be suffice.

I look forward to hearing your answers, thank you.

[Troubled246]

Thank you Doctor.

[Edward W Hook, MD]

The folks on the HIV Prevention Community site are not physicians who specialize in HIV Prevention and STDs, thus it is appropriate for them to cite "official" recommendations, even if those recommendations are based on out of date, overly conservative perspectives from the institutions they represent -better to be overly conservative in such situations.  As for your questions, I will provide brief answers but I wil not engage in a series of "what if", "has it ever" or "how long" questions - they are not productive.  No follow-ups please  :

No risk of HIV from blood draws an when HIV is spread by needles.  It is spread through direct introduction of infected material into the blood stream.

1.  There are no studies to address this issue and there are many variables which impact the survival of the virus- the amount of blood, the temperature, etc.

2.  The thickness of skin on different parts of the body is highly variable. The critical issue is access to the blood stream and the immunological target cells present below the skin surface.

3.  The lancets used for finger pricks are solid and do not carry the same risk as hollow bore needles.  

Please, no further what if questions.  They will not be answered.  EWH

[Troubled246]

Thank you Dr Hook that is most helpful.

I do feel however, that one thing that doesn't help with this confusion and creates a lot of unnecessary anxiety is that the HIV community forum on Medhelp consistently states that 3 months is conclusive, even when people seek assurances and this contradicts what you other expert doctors on this forum and the HIV international forum state.  If you were able to agree a shared consensus view I would imagine that at least a good proportion of worried wells would perhaps worry less.

I wanted to ask about HIV transmission from blood exposures and needles.  I understand the following:

1. No chance of HIV from a blood draw
2. HIV is transmitted through Drug Users because they inject shared needles straight in to their blood stream

But I would appreciate an answer to the following

1. How long does HIV stay active in a hollow bore needle where it is not exposed to the elements (say for e.g in a sharps bin, a dustbin etc), so likely to be in room temperature, but not submerged in water or cold temperatures.

2. Does how deep the needle penetrates your skin make a difference - so would a surface prick that doesn't enter your blood stream be a null and void transmission route? Can you be assured that if you didn't bleed its unlikely even if you were in the unfortunate position of being pricked by a hiv positive needle that this is not a likely transmission route

3. Finally, when you are pricked for a HIV test on your finger, does the lancet go deep enough as a normal hollowbore needle to get that blood, i.e. in to a vein.

Thank you in advance.

[Edward W Hook, MD]

Welcome back to the Forum. I'll try to allay your continuing anxieties.  

1.  HIV DUO tests give definitive results at 4 weeks.  The recommendations for testing at 3 and even 6 months by some agencies are the result of two factors- data from older tests no longer used (you really do not need to worry about which generation of tests you were tested with, at this time virtually all tests are far more sensitive that they were even 2-3 years ago when the 3 month recommendation was made) and secondly, the fact that some, mostly governmental agencies which have to provide recommendations for virtually everyone without the sort of interactions such as those you get with your doctor or on personalized sites such as this one, feel the cannot "afford" to be wrong and therefore make recommendations and guidelines which leave most people unnecessarily nervous for 4-6 weeks longer than the 4 weeks that it takes for DUO tests to provide definitive results or the 6-8 weeks it takes virtually everyone to develop HIV antibodies.  

2.  The tests perform the same, irrespective of the type of exposure.  Risk has nothing to do with it.

3.  I have no idea. In some occupational settings exposed persons are treated with preventative anti-viral therapy (PEP). This can, in theory, prolong the time to eveloping a positive test.  

Bottom line. If you have a 4 week DUO result, believe it. EWH