The prevalence of genetic variants among cases was compared with population-based prevalence estimates for the same genetic variants for the 12-19-year age group available from the National Health and Nutrition Examination Survey (NHANES) III CDC-National Cancer Institute Collaborative Genomics Project databank (10) . NHANES is a nationally representative survey of the US population conducted by the CDC National Center for Health Statistics. During the second phase of NHANES III (1991-1994), leukocytes from participants were used to create a DNA bank maintained by CDC's National Center for Environmental Health that contains specimens from >7,000 participants, including ≈1,200 children. To our knowledge, the NHANES DNA bank is the only currently available source of nationally representative prevalence estimates for genetic variants among US residents. The 12-19-year age group is the youngest age group available in the NHANES DNA bank.