There are tests that can look for the virus—not antibodies—in the blood. Because the virus becomes detectable in the blood much sooner after infection than antibodies, these tests are an option for people who simply can't wait 13 weeks to find out the results of standard ELISA/Western blot testing. And because there has been some encouraging research indicating that people who diagnose their HIV infection early—meaning the first weeks after infection, before antibodies become detectable—can protect their immune systems by starting treatment early, these tests are proving to be very useful for people who recently engaged in a high-risk activity (e.g., receptive anal sex without a condom) and fear they might have been infected.
These tests look for fragments of HIV, either floating around freely in the bloodstream or inside cells in the bloodstream. Some tests—known as qualitative tests—yield a "positive" or "negative" result, meaning that the virus was or wasn't found (GenProbe's Aptima HIV-1 RNA Qualitative Assay is the only test approved for this purpose). Other tests—known as quantitative tests—yield a "viral load" result, meaning the amount of virus in a sample of blood. Roche's quantitative Amplicor HIV Monitor Test is frequently used by doctors and research centers but is not specifically approved for this purpose. It is only approved to monitor to people who are known to be infected with HIV, particularly to find out if their treatment is working properly.
These tests are highly sensitive, meaning that they can detect even the tiniest amounts of HIV in a blood sample. However, they are not always specific, meaning that they can sometimes yield a false-positive result. In turn, follow-up testing using standard ELISA/Western blot assays, is typically recommended.
These tests must be ordered by a healthcare provider, meaning that you should call your doctor if you think you may have recently been exposed to the virus and would like one of these tests. It's also important to keep in mind that these tests can be expensive and are not usually covered by insurance for diagnostic purposes.
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