Only about one in five teenage gay and bisexual males in a new study said they'd ever been tested for HIV, despite their increased risk of infection.

And almost half the teens didn't know where they could go to be tested for HIV, the virus that causes AIDS, researchers found.

"It’s important for all teens to get tested if they're sexually active, but it’s especially important for young gay and bisexual men to be tested because they're at such an increased risk of transmission," said lead author Brian Mustanski, of Northwestern University Feinberg School of Medicine in Chicago.

The U.S. Centers for Disease Control and Prevention (CDC) recommends routine annual HIV screening for everyone between the ages of 13 and 64, and more frequent testing for those at an increased risk.

Recent research suggests that testing rates among young adults are low, and that gay and bisexual men may misjudge their risk of becoming infected with HIV (see Reuters Health story of Oct. 2, 2014 here: reut.rs/1yAOvmy).

Little is known, however, about the screening habits of teenage gay and bisexual men, Mustanski told Reuters Health.

The new findings, published in the Journal of Adolescent Health, are based on data from 302 gay and bisexual males, ages 14 to 18, who were mostly recruited through ads on Facebook.

"We did a brief phone call with them to make sure they were appropriate for the study," Mustanski said. "We had them fill out questionnaires at the beginning."

Overall, about 20 percent of the young men reported ever being tested for HIV. The testing rate was slightly higher, at 30 percent, among the sexually active teens.

Teens were more likely to report being tested for HIV if they knew where to be screened, but only about 43 percent of participants knew of a testing location.

About a third of participants also reported stigma as a reason to forgo testing. For example, they do not want others knowing they were tested.

About a third also believed they are not at risk for HIV infection.

Mustanski said rates of HIV screening are likely low for all teens. "So it’s not just unique to gay and bisexual young men," he said. But that group is among the most at risk for infection.

Mustanski added that there are services available to help young people find HIV screening locations in their areas, like the GetTested program from the CDC (gettested.cdc.gov/).