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What Is a HIV PCR Test?

As part of an HIV PCR test, clinicians use DNA polymerase to amplify pro-viral genomes.
Blood samples are taken from a patient at the start of the HIV PCR test process.
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  • Written By: Karyn Maier
  • Edited By: Bronwyn Harris
  • Last Modified Date: 07 July 2014
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The HIV PCR test is one the most accurate diagnostic tools in use to detect the presence of the human immunodeficiency virus in the blood, more commonly known as HIV. Aside from being considered more reliable in terms of accuracy than most other tests, the HIV PCR test is also one of the few screening procedures that can be used for early detection. Most people can get an accurate test reading three to four weeks after a suspected infection.

Unlike other tests, such as the P24 antigen test, the HIV PCR test does not rely on the presence of antigens or antibodies in the blood for diagnosis. Instead, it endeavors to identify certain genetic material by highlighting sequences of the virus within the subject’s deoxyribonucleic acid, or DNA. This is achieved via nucleic-acid amplification testing to observe the resulting polymerase chain reaction, hence the acronym “PCR.” In addition, the HIV PCR process is further divided into two sub-categories that determine “viral load” in a serum sample: RNA PCR and DNA PCR. The former is used to screen blood donations and the latter is used to detect HIV in infants born to mothers known to have the virus.

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To perform an HIV PCR test, the clinician or technician uses an enzyme known as DNA polymerase to pursue a pro-viral genome sequence and “amplify” it, or trigger viral replication in vitro by several million times within just a few hours. In addition to this enzyme, the PCR-inducing cocktail also contains oligonucleotides and deoxynucleotide precursors, as well as a cofactor called MgCl2. In the early days of this procedure, the genetic material was cycled at gradually elevating temperatures for a specific time. However, the PCR amplification process is now self-regulated through the addition of Taq polymerase, which is derived from a species of bacteria that naturally occurs in hot springs.

Generally speaking, HIV testing is best performed in a clinical setting since it is more conducive to safety and accuracy. However, there are home testing kits available that involve sending off blood samples to a lab under the confidentiality of an assigned code instead of the subject’s name. There is only one such reliable test kit available in the United Kingdom, and only one in the U.S. approved by the Food and Drug Administration. Otherwise, it is not advisable to purchase other so-called home HIV testing kits on the Internet since these haven’t been evaluated for accuracy.

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Discuss this Article

anon310510
Post 11

I took the Hıv-1 rna test two weeks after risky sexual activity and the result is negative. But this result was not enough for me. One week later, I used p24 antigen and antibody test and the result was negative.

My question is, are these tests enough or not?

anon162323
Post 8

The dna pcr is conclusive and is 99.99 percent accurate after two weeks of exposure. So it's like gambling. If you had this test and the result is negative you will be relieved. Otherwise it can have a worse effect after three months but this test is at least 90 percent specific.

anon158361
Post 7

all the negative hype about this test is not valid and false. pcr. dna or rna is one of the top tests out there, and if it is negative, it is a valid and a conclusive result.

anon140752
Post 6

What is the accuracy of this test? Does it really search the virus or only rna or dna? why can this test give results in blood without hiv? Why does Dr. Mullis say it that this test can't search the virus and is made only for determining only a part of it and not all the structure of the virus. So if you have another infection, you can have many copies of viruses, right?

troy1965
Post 5

Are there any PCR tests that can measure a minimum of 5-10 copies? someone being exposed to a female hiv once via sexual intercourse, and found out after two weeks was only placed on PeP after the two weeks and took the PeP for one week. Then had the HIV PCR Qualitative Test at three weeks and was Negative! The pathologist said it was due to the two weeks of no PEeP the HIV PCR would have picked up the virus?

anon121601
Post 3

what does it mean when the PCR test comes back with the "negative" result.

anon119559
Post 2

you are correct. a PCR can come back as undetectable, but that does not mean it is negative and you do not have HIV infection. most viral load tests can measure a minimum of 40 copies in your blood. hence, if you had 20 copies of the hiv virus in your blood, you would still have hiv infection, it is just not picked up by the test. --Dr. Sciberras

anon89488
Post 1

I think it can come back negative and still not exclude HIV infection, right?

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