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Re: HIV Positive or Negative
Sep 30, 2008

Hello. Thanks for the quick response to my question you recently updated at http://www.thebody.com/Forums/AIDS/SafeSex/Archive/Infected/Q196241.html

I forgot to mention, that i'm not sure if they did a confirmation test (such as a western blot test) or any other testing. I assume they did, as they drew lots and lots of blood from me, and this is a rather large medical insitution.

I have gone and got another blood elisa test as of (08/29/2008)

Some remaning questions or thoughts.

1. What is the difference between a ELISA and Western Blot test? How long does it take for a Western Blot test to show results?

2. If a western blot is positive, can your elisa be negative at any time?

3. If you started medicine in the acute period, can it cause a negative elisa test?

I have had three rapid HIV tests within the past week. (all negative) However, I have been on medicine for two 1/2 years now.

Response from Dr. Frascino

Hello,

1. See below regarding the difference between ELISA and Western Blot tests. The Western Blot is an anti-HIV antibody test and therefore, just like the ELISA, it requires three months from the time of the last exposure to be considered definitive.

2. Yes, you could have a false-positive Western Blot. And that is why you should never run a Western Blot without first getting a positive ELISA. Said another way, if your ELISA is negative, you should not get a Western Blot.

3. No.

Your three negative HIV tests are a very good indication that you are (and always have been) HIV negative.

Dr. Bob

Dr Robert is an Hiv WesternBlot (ELISA versus WESTERN BLOT tests for diagnostic screening) Sep 29, 2008

Dr Robert is an Hiv Western Blot alot better then reg HIv 1/2 Elisa. Yeah I had My Dr run them both tests and they are Negative. Thanks'

Response from Dr. Frascino

Hello,

Western Blot tests should only be run to confirm a repeatedly reactive (positive) ELISA (or EIA or rapid test). It should not be used as a diagnostic tests without a positive initial screening test, due to the possibility of false-positive or indeterminate Western Blot results. This has to do with the sensitivity and specificity of these two tests (see below). You can learn much more about HIV testing by reviewing the chapter "HIV Testing Basics" that can be easily accessed on The Body's homepage under the Quick Links heading. Check it out!

Dr. Bob

ELISA

The ELISA (also sometimes called EIA) is almost always the first screening tool; it is inexpensiveand very sensitive for detecting the presence of HIV antibodies. In most cases, a blood sample is tested, but other types of ELISAs that use saliva and urine have also been developed. The actual ELISA takes 3.5 to 4 hours, but most test sites send samples to outside labs, where they are tested in batches, so you may have to wait one to two weeks for results. Beyond the "window period," ELISA tests are very rarely "false negative." This means if you have a negative test result, and you were tested at least six months after the last potential exposure, you are really HIV negative. An ELISA test may rarely be "false positive." False positive ELISA results can occur if someone is tested right after events that temporarily stimulate the immune system, such as viral infections or immunizations. They could also occur because of lab error, or because of the test's very high sensitivity, discussed below. For these reasons, positive ELISA results must always be confirmed with a Western Blot or IFA (below), and at reputable test sites this is commonly done automatically -- meaning you don't have to have another blood sample drawn. A relatively new test, called a detuned ELISA, which has been used in research settings, will soon become more widely available to other test sites. The detuned test, which is used only after HIV antibodies are confirmed by a Western Blot test, can determine if the HIV infection is recent (within the last six months), which may be useful for deciding upon possible early treatmentoptions.

Western Blot (WB) Assay

The WB is a confirmatory test: it is only performed if the ELISA is positive. The WB can be positive, negative, or indeterminate. Indeterminate tests are neither positive nor negative. An indeterminate result usually means that a person has just begun to seroconvert at the time of their test. In the rare cases in which this occurs, the person will need to be retested, usually about one month later. False positive results are extremely rare with the WB, so it confirms (proves) that HIV antibodies are present.

False Positive Sep 28, 2008

Hello. First, I would like to thank you for a great website. Your content, ease of use and dedicated honest questions i'm sure have helped thousands in the understanding of HIV/AIDS.

In February of 2006, I went to a local clinic to get tested for HIV. My HIV occurance happended sometime in the month of January/Early February of 2006. I had flu like systems in February of 2006. On March 9, 2006 the local health department called me to let me know my result was positive. The RNA test had returned positive, while the elisa test returned negative. They immediatley provided care at the doctors office and they began me on Sustiva/Truvuada.

I have now been on Sustiva/Truvada (switching over to Atriplia) from March of 2006 to the present. My cd4 count was 500 with a viral load of 20,000. The following month, of April, 2006, my viral load was undetectible. My viral load has always remained undetectible with a cd4 count averaging 600.

This week, I went and got a oralquick HIV test just (09/23/2008) and the test result was negative. Confused, I was.

To confirm, I went and got another HIV oralquick test on (09/25/2008) which I made they perform two tests on me at the same time. Both of those tests came back Negative.

My question of disarray is i'm positive or negative?

I do not know if the treatment center ever did a confirmation test on me. I always assumed they did.

Additionally, could of the medicine, for lack of better words, "cured" me?

Why was there a viral load in the beginning and a lower than my average of CD4 count?

Thanks for your assistance.

Response from Dr. Frascino

Hello,

A clinic told you that you were HIV positive based on a PCR RNA test that showed a low HIV plasma viral load and a negative ELISA test!!! YIKES!!!! I can only assume that the clinic felt you were undergoing acute retroviral syndrome (ARS) and were still within your window period (defined as the first three months after primary HIV infection). That is the only scenario that could account for their advising you that you are HIV positive despite having a negative ELISA. However, because HIV PCR RNA tests have a significant rate of false-positive test results, especially at low viral loads, they certainly should have followed up with confirmatory HIV-antibody tests once you were out of your window period. That you have now have had three separate negative rapid tests out three years from your "diagnosis" indicates your initial HIV positive diagnosis may have been (and probably was) wrong. I would strongly advise you have an evaluation with a competent HIV specialist to sort this situation out definitively. If you need help locating a certified HIV specialist physician in your area, check the American Academy of HIV Medicine's Web site at aahivm.org. There you will find a roster of certified HIV specialists listed by locale.

Could the medicine have "cured" you? No, unless you believe in miracles. The much more logical explanation is that your initial HIV PCR RNA was a false-positive.

Write back and let us know how this all settles out. It's an excellent lesson for our readers and a clear demonstration why I consistently advise that HIV PCR RNA (or DNA) should not be used for routine diagnostic screening!

Good luck!

Dr. Bob



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