Study Guide week 9
3 types of HIV tests
1. Indirect tests (ELISA) 2. Antigen/Antibody combo tests (Fourth generation tests) 3. Direct test (NAT)
What is an advantage of testing oral mucosa or urine for HIV instead of using a serological test?
quicker results once test is taken, because 30% of people tested thru ELISA do NOT return to get results. oral and urine tests deliver much quicker results
Even though the development of an HIV test was a great advancement in the history of HIV, why would individuals chose not to get tested? (circa 1985)
some people may not have wanted to know they had the virus, they think they may not be at risk for virus, they do not want to know if they are infected and deal with having HIV, maybe it was not offered to them by doctor and they are afraid to ask
What is the general testing schematic? In other words, if you test positive for HIV in your first test, is that it?
If negative, maybe check again in case of a false negative. If positive, take another test to make sure not a false positive, if still positive, talk to a healthcare provider about starting HIV treatment
indeterminate
test did not give a clear negative or positive result
Why are NAT used on infants? (In other words, why not use the antibody test?)
the NAT test can be used with dry blood from infants, not as invasive as antibody test
Why might NAT be necessary once we have an HIV vaccine?
NAT detects for virus itself, not just antigens/antibodies, which can give false negatives/positives. NAT tells for sure if someone has the virus and also the amount of virus, useful when administering HIV vaccine (once found) to tell which patients need what
How does a direct test (NAT) differ from the ELISA? [e.g., what does it test for, advantages/disadvantages, when can it be used to confirm infection?]
NAT tests detect actual presence of virus, instead of the antibodies produced in response to the virus like the ELISA test. indirect test does not give a clear picture of viral presence. window period: 10 days after infection (10-33 days)
ELISA (enzyme-linked immunosorbent assay)
an indirect HIV test- detects antibodies produced in /response/ to HIV. used commonly, highly accurate, low cost, developed in 1985.
How does an ELISA work to detect HIV? When can it be used (accurately) to determine infection following exposure (window period)?
an indirect test- detects antibodies produced in /response/ to HIV. window period- 23-90 days
Why is the antigen/antibody combo test becoming the preferred initial HIV test over the antibody test alone?
can detect infection earlier, HIV making proteins (antigens) before body makes antibodies
antigen/antibody test
detects HIV antigens and HIV antibodies. is a serological test. window period- 18-45 days
NAT/viral load test
detects actual presence of virus. NAT detects HIV nucleic acid. known as viral load test since the amount of virus in the blood can be quantitated.
false negative
initial test nonreactive despite presence of HIV antibodies or antigens in blood. reason: window period variations
false positive
initial test reactive, but no reaction found at later testing. reason: some other antibodies have been known to react with HIV antigens
What are the benefits of rapid testing? Do rapid tests change the window period of the test?
less invasive than other tests, quicker results once test is taken, 1-20 mins, these tests do not change window period, just the results after test is taken is much quicker.
seroconversion
the period of time during which HIV antibodies develop and become detectable. you're either seronegative or seropositive
window period
the time between when a person may have been exposed to HIV and when a test can tell for sure whether they have HIV
What are some of the reasons it is important that people get tested for HIV?
your own health, the health of those you have contact with, to be aware of your body and what you are doing with it. better knowledge of the subject when more people know about it
