Less than a quarter of adolescent men who have sex with men, or AMSM, have ever been tested for HIV despite being at higher risk for infection, study findings suggested. According to Brian Mustanski, PhD, director of the Institute for Sexual and Gender Minority Health and Wellbeing at Northwestern University, and colleagues, an estimated 51.4% of adolescents aged 13 to 24 years with HIV are undiagnosed, compared with 14.5% of total HIV infections in the United States.