Rapid Oral HIV Test (cont.)
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What Are the Advantages of a Rapid HIV Test?
The rapid test allows for testing of more individuals. According to the CDC, 1.2 million Americans have HIV, but up to one in eight don't know it. About 44,000 Americans per year become infected with HIV. This number has decreased recently due, in part, to more testing. Among those who get tested using traditional (non-rapid) methods, 31% of those who test positive do not return for their results (which are typically available one or more weeks after the test is done).
People give a variety of reasons for not returning for their test results. The frequency of each response depends on the population being tested. The most commonly given reasons include the following:
Significant benefits of the rapid HIV test include the following:
Both conventional and rapid tests can be further divided into third-generation antibody tests or fourth-generation combination antigen/antibody tests. The third-generation antibody tests detect antibody to HIV, which is a protein that the body makes in response to an HIV infection. The fourth-generation tests both antibody and antigen, which is a protein of the HIV virus itself. The main difference between the third- and fourth-generation tests is the "window period" or how quickly after a new infection the test can show positive results. The window period for current third-generation tests is 22 days, meaning it could be as long as 22 days between the time of infection and the test showing a positive result. The window period for the fourth-generation tests is as much as one week. People who take an HIV test during the window period after a possible exposure to HIV are advised to come back later to take another test.
Once important difference between the conventional laboratory test and rapid tests is the ability to detect very early or acute HIV infection. This is done with the addition of an HIV RNA PCR or NAT (nucleic acid amplification) test. HIV RNA appears in the blood within the first few days of infection. If the antibody test is negative but the NAT is positive, this may indicate that the patient is very newly infected. NAT testing is also used to confirm a positive result of the third- or fourth-generation test. Western Blot testing is no longer routinely used.
Medically Reviewed by a Doctor on 9/21/2016
Steven Fine, MD, PhD
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