Anonymous
Could you please explain the difference between the Qualitative vs Quantitative PCR RNA HIV tests? I have heard that these tests are not FDA approved for diagnostic purposes as well as prone to false positives. However, I do not want to wait for 12 weeks for Western Blot antibody test, I want faster results. Should I choose Qualitative or Quantitative PCR RNA?
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Anonymous
Hello,

Thank you for contacting AIDS Vancouver. I see you have some questions about HIV testing. I will provide you with our test chart and some additional information about these tests to help you make a decision about what test to take.

First there are tests available such as the 3rd generation test or the Rapid Test that can be done at a clinic or testing site as soon as 4 weeks after your exposure to the virus.These tests can detect up to 95% of new infections starting at 4 weeks after exposure although a follow-up test at 12 weeks is still recommended for conclusive results. Depending on your location you may also have access to a 4th generation combination test which can be taken after 4 weeks and while in Canada guidelines state it is conclusive at 12 weeks, many experts consider a 6 week test to be conclusive.

In regards to the PCR tests these tests are most often used to screen infants born to HIV positive mothers for the virus, or to screen blood and organ donations for the virus. They are not typically used as diagnostic tests. Similar in this regard is the Western blot which is typically used as a confirmatory test rather than a diagnostic test. Qualitative PCR tests for whether any viral genetic material is present, whereas quantitative PCR tests for the amount of viral RNA present.

There is a selection of tests available to you, there are several options aside from PCR and Western blot tests. The 4th generation test if you can access it is likely your best option for fast results, though we still recommend a 12 week follow-up test.

EIA 3rd Generation

RAPID
Test Name Method Window Period Conditions
Enzyme Immunoassay Antibody (EIA) 3rd Generation (ELISA) Blood test that looks for antibodies. Up to 95% of infections are detectable within 4-6 weeks post exposure. Most people develop detectable antibodies in 21-25 days. Most commonly available testing method. Conclusive at 3 months post exposure.

POOLED RNA NAAT
Test Name Method Window Period Conditions
Rapid or “Point-of-Care” Blood or oral swab test that looks for antibodies. Up to 95% of infections are detectable within 4-6 weeks post exposure. Most people develop detectable antibodies in 21-25 days. The rapid test is a type of 3rd Generation test. Two forms available: finger prick blood sample or oral swab. Oral swab test is most common in the U.S. but due to false positives in Canada it is not approved and blood collection is more likely. Many places in the U.S. and abroad may charge a fee for rapid testing. Conclusive at 3 months post exposure.

NAAT (PCR RNA & DNA)
Test Name Method Window Period Conditions
Pooled RNA NAAT or “Early Test” Detects viral RNA in blood of people who have yet to develop detectable antibody levels. 10-12 days post exposure The pooled RNA test is often expensive and not readily available. One must be referred by a health care professional to receive this test. An antibody follow up test after 12 weeks is sometimes necessary depending on how long after the exposure the test was performed. Conclusive at 3 months post exposure.

P24 Antigen
Test Name Method Window Period Conditions
NAAT (PCR RNA & DNA) Nucleic-Acid Amplification Testing (NAAT) looks for the genetic material of HIV and tests for it with a Polymerase Chain Reaction (PCR) test. 2-3 weeks post exposure NAAT tests generally take two forms: DNA PCR and RNA PCR tests. DNA PCR NAAT tests are usually used for screening babies of HIV+ mothers. RNA PCR NAAT tests are often used to screen blood or organ donations. Both measure the viral load of a positive person’s blood. Conclusive at 3 months post exposure.

Western Blot
Test Name Method Window Period Conditions
P24 Antigen The antigen on HIV that most commonly provokes an antibody response is the protein P24. This test looks for this protein. ONLY within first few weeks after infection. Once the body starts producing antibodies, the antigen is no longer detectable. This test is part of the 4th Generation EIA test, which most specialists agree is conclusive at 6 weeks. Official guidelines recommend re-testing at 12 weeks with an antibody test. Accuracy: see 4th Generation EIA tests.

4th Generation EIA
Test Name Method Window Period Conditions
Western Blot Immunoblot which detects HIV antibodies directed against specific HIV proteins. Interpreted according to Canadian consensus guidelines. 4-6 weeks (may take up to 8 weeks for a positive result) The Western Blot test is only used to confirm a positive test result and it considered to be the "gold standard" for confirmation of HIV infection. If test results are indeterminate, PCR NAAT Tests are usually performed to confirm an infection. Conclusive at 4-6 weeks post exposure.

Home Testing
Test Name Method Window Period Conditions
4th Generation EIA Blood test that looks for antibodies AND p24 protein antigens. Commonly referred to as the "combination," "combo" or "DUO" test. P24 protein is detectable immediately after infection but only for the first few weeks. The antibody (ab) test has a window period of 4-12 weeks post exposure. This test is widely available in North America. Most HIV specialists consider this test to be conclusive at 6 weeks but official HIV testing guidelines still recommend re-testing at 12 weeks for conclusive results. Conclusive at 3 months post exposure.

So in summary there are a variety of tests available, I hope that this information will help you to make an informed decision.

Best regards,

Alex

AIDS Vancouver Helpline/Online

Monday-Friday 9am-5pm (PST)

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Test Name Method Window Period Conditions
Home Testing Oral swab or finger prick blood test. Unknown Home testing is not approved for use in Canada and is not endorsed by AIDS Vancouver. Home testing frequently results in false positives and negatives and does not provide an opportunity for pre- and post-test counselling.