Avatar universal


Is there a certain time after the window period where the DNA PCR test will NOT detect HIV?

I've read all the posts about getting an antibody test, however will a PCR test still detect the virus after 2 months or 3 months, or is that simply too late for the PCR to detect the virus anymroe?
8 Responses
Avatar universal
Reread the replies you have been given.
1364665 tn?1291607092
"Qualitative PCR tests

The DNA Qualitative PCR is not FDA approved diagnostic test. Although it can often pick up an infection after about one month after an exposure, it will not always detect the infection. It is NOT designed to do routine screening in adults. It is used primarily for:

   1. Research applications, where the test can be repeated multiple times to rule out inaccuracies.

   2. Testing in babies less than 18 months of age, where antibody tests are not reliable.

   3. Testing in persons with other diseases of the immune system where antibody tests may not be reliable.

   4. Testing in persons who repeatedly test indeterminate on antibody tests. An indeterminate antibody test occurs when these tests cannot determine whether a person is infected or not. Indeterminate antibody tests occur very rarely.

   5. Other UNUSUAL circumstances.

When we do Qualitative Diagnostic PCRs, we often do them more than once (and often in combination with other diagnostic tests, like antibody tests), just in case the test did not give an accurate result. This test is very difficult for labs to perform, and it is therefore very expensive. The more difficult the test, the more the chances for inaccurate test results. If the test is done just right, it can give an accurate result. But because it is difficult for labs to do, there is a greater chance for inaccurate results (as compared to antibody tests). Usually only regional reference labs will do this test, not the vast majority of clinical labs.

Many people have requested these tests, since they do not want to wait three or six months to take an antibody test. Doing these tests is clinically not necessary in the vast majority of these cases, and only needlessly increases our health care costs (these tests often cost several hundred dollars). In the vast majority of cases, antibody tests are all an adult needs. If a person cannot cope with the three or six month waiting period for antibody testing, counseling is often a better option than PCR testing.

There is a specific additional situation (other than those listed above) when the PCR test can be used for diagnostic purposes, as discussed in the paragraph below. "

Dr. Rick Sowadsky
Avatar universal
Thanks  but no one answered my question. Can this test detect the virus at 3 months just as well as it can at 1 month?

I understand that antibody tests are the only FDA approved diagnostic test, and this is mainly so because of the costs involved with PCR and their overly sensitive results that can result in too many false positives.

Still the question remains, can this PCR test detect virus after a significant amount of time past 28 days or does the virus drop to undetectable levels for this test?
Avatar universal
We are not going to discuss unapproved tests.
Avatar universal
Can anyone answer my question? Thanks!
Avatar universal
To my knowlegde after seroconversion takes place and antibodies are detectable, the PCR will not be able to detect the virus due to drop in viral load. but I am not a scientist or a doctor. I would listen to the doctor and understand the answer to your question is complicated. Whether or not theres a definitive answer to that question  it really has no bearing on your final HIV status. It is not a good diagnostic tool. It might help to know why you are so set on that one question. Did you get a test result after 28 days from a PCR that was negative and you are worried that it might not have picked it up? Just get an antibody test. It is my understanding that even if  PCR test is positve it is not a conclusive result for diagnosis and will have to confirmed with an antibody test at the appropriate time frames.

THere is a exerpt from a website below that answers your question .

Antigen test (P24 test)
Antigens are the substances found on a foreign body or germ that trigger the production of antibodies in the body. The antigen on HIV that most commonly provokes an antibody response is the protein P24. Early in HIV infection, P24 is produced in excess and can be detected in the blood serum (although as HIV becomes fully established in the body it will fade to undetectable levels).

P24 antigen tests are not usually used for general HIV diagnostic purposes, as they have a very low sensitivity and they only work before antibodies are produced in the period immediately after HIV infection. They are now most often used as a component of 'fourth generation' tests.

Avatar universal
That is true of the antigen test, but the PCR test detects the actual virus. Still no real answer but I appreciate the help!
Avatar universal
Sorry I confused the two, I think they use the PCR test to test blood supplies, so in that case I would think yes it would continually be detected throughout the life of an HIV+ person.
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