But some doctors warn that sometimes a negative test can give a false sense of security to both doctors and patients, particularly for risk-taking teenagers, said Dr. Allison Agwu, a pediatric infectious disease specialist at Johns Hopkins Children’s Center.

Rapid HIV tests are designed to pick up antibodies to the virus, not the virus itself. It can take weeks or months for someone to produce antibodies. So a rapid test can come up negative the first time, but positive some weeks or months later. False negatives often happen during the earliest and most contagious stages of the infection.

Of the 53,000 new HIV infections diagnosed each year in the United States, 14 percent of those occurred in 13 to 25-year-olds, according to the Centers for Disease Control and Prevention and the CDC reported last week that nearly half of all HIV positive teens don’t know they have the virus.

For the full article, please refer to http://weblogs.baltimoresun.com/health/2009/07/teens_hiv_testing.html