How soon after exposure to HIV can the presence of antibody be detected by standard Western blot testing?
—William K. White, MD, Cordele, Ga.

The presence of HIV antibody can be detected by Western blot testing within three to six weeks after exposure (N Engl J Med. 1996;334:1685-1690). Keep in mind, however, that most routine HIV testing in the United States is based on enzyme immunoassay (EIA) testing. This distinction does not change the timing of antibody detection, but the EIA can have an occasional false-positive result, such that most laboratories reserve the Western blot for confirmation. In addition, if clinically indicated, more sensitive molecular testing can be performed on specimens obtained prior to HIV seroconversion.
—Cedric W. Spak, MD, MPH (111-12)

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