The ELISA test is a powerful tool for detecting the presence of antibodies to HIV in the blood. It was first developed by Dr. Edward Laumann, and it's been used for more than 20 years now to diagnose HIV infection. The test has two benefits: It's very sensitive, meaning that it can detect even very small amounts of antibodies in the bloodstream; and it's also very specific, meaning that it rarely gives false positives or false negatives.
The ELISA test has been in use for more than 20 years now, and it is still the most comprehensive diagnostic tool for HIV that we have.
In an ELISA test, you would be asked to provide a blood sample at your doctor's office or medical clinic. The sample will then be sent to a lab where technicians will test your blood sample using an ELISA kit (which is actually just a box containing all of the necessary items needed for this type of testing).
The technician will take some of your blood and add it to two different solutions: one solution contains antibodies against HIV; another solution does not. If there are any antibodies present because you have been infected with HIV, then those antibodies will react with either one or both solutions depending on whether or not they are able to bind to proteins contained within them.
The sensitivity of the ELISA test allows it to detect antibodies to HIV-1 or HIV-2 in virtually all infected people. This means that if you're infected, your ELISA will come back positive, even if your symptoms are mild or non-existent, or if you've been taking medications such as AZT (Zidovudine) for a long time. It cannot be affected by other conditions that may cause similar symptoms and can't be affected by other infections such as hepatitis C virus (HCV).
The ELISA is also very specific. The specificity of the ELISA test is 99.5%. This means that if you have a positive result on an HIV test, it's highly unlikely that you don't actually have HIV. In other words, very few people with a false positive result will get that result on this test!
The ELISA test is especially accurate when used on blood samples from people who have had symptoms of HIV. It's also more reliable if the person has been exposed to HIV recently, and for people who have had unprotected sex with someone who was infected.
If a positive ELISA result is followed by a confirmatory Western blot test, the accuracy increases to 99.5%. This is because the ELISA is more sensitive than the Western blot but less specific. In other words, it's easier for someone who doesn't have HIV to get a false positive from an ELISA test than it is for someone who does have HIV to get a false negative from one. But since both of these tests involve examining proteins attached to antibodies in your blood samples, if you're pregnant or taking any medications that affect your immune system (like corticosteroids), then there are likely proteins present in your blood that might cause confusion when testing for antibodies against HIV—and these can lead to more false positives than usual.
The ELISA test is an extremely accurate technique, but it’s not perfect. False positive results can occur if a sample is taken too soon after exposure or if the sample is contaminated with antibodies from another source.
If you have been exposed to HIV and test negative, it’s possible that your body hasn't made enough antibodies yet for them to be detected in your blood. It also might mean that you don't have enough of them circulating in your bloodstream yet for the ELISA test to detect them. However, this doesn't mean that you're “not infected." Your body could still be producing these substances at higher levels than the ELISA test can detect (or in smaller amounts), so it would still be wise to get tested again at some point in the future when more antibodies are present—ideally within 12 months of exposure.
In addition, certain medications may cause false positive results because they interfere with how well an antibody-based test detects HIV infection
The ELISA test is not foolproof, however: false negatives are possible.
In fact, a false negative result can occur if the sample is taken too soon after exposure. This means that even though you may have been exposed to HIV, your body is still in the process of building antibodies against it and your blood will not yet have detectable levels of these antibodies.
Another reason for a false negative result has nothing to do with the test itself but rather how it's conducted. In order to perform an accurate test on yourself or someone else (including newborns), samples must be taken with sterile equipment by trained professionals who understand how best to collect them correctly. If you're using home testing kits or taking samples from yourself at a non-clinical location like an STD clinic or Planned Parenthood office (which won't necessarily use sterile equipment), there's no guarantee that your results will be accurate.
The ELISA is a test that uses antibodies to detect HIV in the blood. It’s been widely used since it was developed by Western blot in 1985, and today it’s one of several types of tests available to diagnose HIV infection.
The ELISA is also considered a highly accurate diagnostic tool—especially when used properly.
Overall, the ELISA is a very reliable test for detecting HIV antibodies. It is especially accurate when used on blood samples from people who have had symptoms of HIV. False negative results can occur if the sample is taken too soon after exposure, or for another reason that has nothing to do with the test itself. If a positive ELISA result is followed with a confirmatory Western blot test, the accuracy increases to 99.5%. Only five out of every 10,000 healthy individuals will have a false positive result.