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Testing Information

Dr. HHH

When you refer to 6-week HIV test being 99-100% conclusive, does this include testing with the OraQuick Advanced Oral test?

Will both HIV-1 and HIV-2 produce antibodies at the same rate? Thus, does the 6-week timeline hold for both types of HIV?

Many people mention a Generation 4 ELISA test. I have done a lot of hunting and have been hard pressed to come up with testing locations for this (including my own GP and the local STD hotline); can you recommend somebody who does these tests?

Thanks

5 Responses
239123 tn?1267651214
MEDICAL PROFESSIONAL
Yes, the figures hold for both Oraquick oral and the "4th generation" ELISA tests, and for both HIV1 and 2.  (HIV-2 is so rare in the U .S. that it doesn't much matter; indeed, some public health clinics don't even include HIV-2 in routine HIV testing.)  "4th generation" isn't a trade name; it simply refers to the latest technology for antibody testing, and is the basis for most routine HIV tests now used in the U.S.

Good luck-- HHH, MD
Avatar universal
Doc,

I had posted several weeks ago about a trip to China where it was protected sex with a condom but still ended in NSU. Since then I had the flu and 2 weeks later still have a sore throat and bad headaches. I know, coincidence but, it's enough it get me worked up.

Through a series of negative PCR (HIV-1) tests and a negative OraQuick at week 5.5 I feel good about that virus but still worry about HIV-2 which is on the rise in China.

Can you provide the source of the data that supports the 6 week 99-100% conclusive?
Avatar universal
When Dr. HHH states that a 6 week HIV test is conclusive, I believe that is his professional opinion based on his extensive training and experience with STDs.  I do not believe anyone will be able to produce a reference for that information.  The New York State Department of Health has a website where they provide HIV information in the form of questions and answers.  The response to question 39 states "With the HIV antibody tests used in New York State, virtually all people who are infected will test positive within one month of being infected.  Most people will test positive even sooner."

I believe a 4th generation test is a combined p24 antigen test with a 3rd generation ELISA antibody test.  I do not believe that a 4th generation ELISA test is available.  

It may be a bit too strong for the doctor to state that most routine HIV tests in the U.S. use this technology.  Home Access is a first generation test, and LabCorp (where my doctor sent my blood for testing) uses a second generation test.  I tested negative at 8.5 weeks which I take to be definitive.  As others have pointed out on this forum, the generation of the test is not that significant at 6 weeks and beyond.  

The doctor has previously stated that he has never seen anyone who tested negative at 6 weeks later test positive, unless there was another exposure involved.  From the websites I have read, a first generation test will detect HIV antibodies about 5 to 10 days later than a third generation ELISA test, and a second generation test will detect antibodies somewhat sooner than the first generation test.  

I'm quite confident that you are HIV negative based on your test results.  But if you are not sure (especially for HIV 2), you may want to retest in the future.  Note that the third generation ELISA test does include HIV 2, whereas the first two generations do not.  

I hope this is helpful.  Good luck.
Avatar universal
The sentence "In such cases, the odds HIV is present are greater than the risk dying from natural causes or an auto accident in the next 24 hours" should say "less than", not "greater than" (as probably is obvious to all but the most OCD readers!).  Excuse the typo.

HHH, MD
239123 tn?1267651214
MEDICAL PROFESSIONAL
What everyone forgets is that there are few cases of HIV in which the exact date of exposure is known.  When test performance at various intervals is calculated, it depends on the accuracy of the tested person's memory and often guessing which of several possible exposures was the actual source.  The large majority of infected people are at overt high risk with multiple exposures and contacts, so the exact infection date rarely is known with certainty; exposures often occur in settings of alcohol or drug use; and human memory is fallible.  (Most HIV infected people are not like those who post questions on the STD forum, who typically have had a single exposure of low to zero risk.)  The exposure date often is known for transfusion-related infections and in newborns exposed to infected moms, but infection by blood or organ donation is vanishingly rare and there are no useful data with the later generation HIV tests; and the immune system of newborns is too immature to allow such data to be applied to HIV-exposed adults.

To some extent, seroconversion time can be addressed by testing for HIV RNA by PCR, then looking at the speed of seroconversion in people who are PCR-positive but antibody-negative.  But there just aren't very many such people.  Animals can be infected in the lab and their antibody responses studied, but it's a no-brainer than application of animal data to humans carries its own difficulties.

Therefore, estimates that say seroconversion occurs in any particular percentage of cases (95%, 97%, or 99% etc) at various intervals (6 wk, 3 mo., etc) are just that--estimates.  Clearly there are some people who acquire HIV and do not seroconvert for as long as 6 months.  (According to a colleague who is a true HIV testing expert, who I emailed about this yesterday, the probable mechanism is that in rare cases the virus remains inside white blood cells or other tissue cells, not breaking out into the bloodstream; and bloodstream exposure may be required for development of measurable antibody.)  This probably occurs in no more than 1% of infected persons.

When you ask experts who take care of many HIV/AIDS patients (which I do not), everybody is aware of these facts and issues, and understands that delayed seroconversion is a theoretical possibility.  But I have never spoken with one who could recall any patient they cared for in whom this happened in the past 5 years, since the current generation of highly sensitive HIV tests came into wide use.  This doesn't mean it can't or doesn't happen, but it implies it is a rare outcome.

When a person presents a story that implies almost zero risk of HIV acquisition, say a 1 in 100,000 risk of infection (which may be a high estimate of the risk for most questions on this forum), a test with "only" 97% sensitivity reduces that person's risk of having HIV, after the negative test result, to 1 chance in 3 million; at 99%, it's 1 in 10 million.  Hence my frequent comments comparing the odds to lotteries and lightning strikes.  In such cases, the odds HIV is present are greater than the risk dying from natural causes or an auto accident in the next 24 hours.

Bottom line:  Nobody knows with certainty the exact seroconversion rates at various intervals.  Some agencies and experts take a conservative stance (e.g., CDC's 97% at 3-6 months, or whatever it says) and others take a more reassuring stance, especially when dealing with frightened people (e.g., my "virtually 100%" estimate beyond 6 weeks).  It's a judgment call; and the differences reflect reasonable variations among reasonable people.

HHH, MD

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