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Tuesday, July 29, 2014
HIV and AIDS
Can An HIV+ Individual Test Negative For a Year?
Under what conditions could the HIV virus evade a combination of standard (antibody) and HIV/PCR test after one year waiting window?
Typically when you test for HIV we use several different types of tests. First we use an antibody screening test called an ELISA. This measures antibodies that a person makes against HIV. If this test is positive then we confirm it again and send the specimen for further testing. Typically, this is done looking again for antibodies to specific parts of the virus. This technique is called a western blot. These tests typically are positive after 28 days to 3 months. It is unusual not to develop antibodies after 6 months. There are few, if any reports of clear HIV exposure and then development of antibodies a year later. What sometimes happens is that the antibody tests are incomplete or "indeterminate". This means that not all the antibodies are clearing reacting to specific virus proteins on the western blot test. In these circumstances, measuring the virus itself by a technique called "RT-PCR" usually finds the virus. This test measures the presence of virus genes in the bloodstream. I am not aware of any credible reports of persons with true HIV exposure who had all of these tests negative after 1 year. Sometimes, tests may be indeterminate but not usually negative.
Carl Fichtenbaum, MD
Professor of Clinical Medicine
College of Medicine
University of Cincinnati