The Centers for Disease Control and Prevention (CDC) has recommended a new HIV testing protocol for laboratories that will take advantage of advances in testing technology and will better identify acute cases of the virus. The announcement was made to coincide with National HIV Testing Day on June 27.
New “fourth generation” HIV tests not only screen for antibodies to the virus in blood samples but also for what’s known as the HIV-1 p-24 antigen, which shows up in the body much sooner than antibodies. By recommending the fourth generation tests as the first step in the new testing protocol, the CDC will effectively reduce the “window period” during which false negatives are likely. The new tests will detect an infection by about three weeks following exposure to the virus; with the older HIV tests, the window period could be as long as three months. Correctly identifying acute cases of HIV is crucial for HIV prevention because viral loads are typically very high during that period of infection, making someone much more likely to pass on the virus.
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