The most accurate and reliable diagnostic tool used regularly is lab tests that look for HIV antibodies and the p24 antigen.
They are "fourth-generation" tests, meaning that the technology used in them is more advanced than earlier tests.
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What Happens When a Person Gets HIV?
When a person gets HIV, their body makes antibodies against HIV.
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In the weeks after being exposed to HIV, the immune system recognizes some of the virus's parts and starts to make HIV antibodies to hurt, stop, or kill the virus. This time is called "seroconversion." These antibodies will always be there.
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A structural protein called p24 is an HIV antigen. It makes up the majority of the HIV viral core.
During the short time between getting HIV and seroconversion, there are heightened levels of p24 in the blood, but then they go away. Since the p24 antigen is typically found several days before HIV antibodies, a test that can discover p24 has a somewhat shorter window period than a test that detects just antibodies.
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The Newest Research and Information on HIV Tests
The plasma or serum is usually used for 4th-generation combination exams (2 components of blood, detached from whole blood using lab equipment). A needle takes a small amount of blood from a vein in your arm. In a machine in a lab, samples from several different people are analyzed simultaneously.
Like all screening tests, confirmatory tests must be done to check a reactive result, which is a preliminary positive test.
You may also hear these tests called ELISAs (enzyme-linked immunosorbent assay).
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Both the 1st-generation and 2nd-generation lab tests aren't used any longer. The 3rd-generation lab test only looks for antibodies and isn't recommended for use.
Some tests are also called "fifth-generation" tests. They find similar biomarkers but can also tell which samples are positive for p24 antigen and which are positive for antibodies. They can also tell the difference between HIV-1 and HIV-2.
Window Times and Precision
During the window period, right after infection, tests may not always be able to find antibodies or p24 antigen, giving a false negative result.
It is difficult to say exactly how long the time period for a test is because it varies from person to person and is a hard subject to study (recently infected individuals would need to know precisely when they were exposed to HIV and then give multiple blood samples over the following weeks and days).
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Still, the median window period for fourth-generation tests is thought to be 18 days, and half of all infections are found between 13-24 days after exposure.
Even though sometimes this period is a little longer, 99% of HIV-infected people can be found within 40 days of being exposed.
Are Fourth-Generation HIV Lab Tests Reliable?
The fourth generation of lab tests is very reliable.
The most important ways to measure accuracy are sensitivity (the number of times a test is positive when HIV is present) and specificity (the percentage of correctly negative results when HIV is not present).
Conclusion
The fourth-generation tests are very accurate and sensitive. They are more likely to find an infection early than quick tests. They should be used when results don't need to be given right away and when people are likely to come back to get their results.
Quality control programs are easier to set up when a central lab does testing.
Do you have more questions about HIV? Need to know more about HIV symptoms and testing? Click the link here to learn more about HIV tests and HIV symptoms on Blackdoctor.org.
