U.S. Sprinter Debbie Dunn Banned Two Years for Doping (Reuters) - Former American world indoor 400 metres champion Debbie Dunn has been suspended for two years after testing positive for a banned anabolic steroid at June's Olympic trials, the U.S. Anti-Doping Agency said on Tuesday. Dunn, 34, finished fourth in the 400 metres at the American trials and was a member of the U.S. Olympic 4x400 metres relay pool before withdrawing after learning of an abnormal sample. The 2010 world indoor 400m champion was disqualified from all competitive results subsequent to June 22, 2012. Reporting by Gene Cherry in Raleigh, North Carolina; Editing by Frank Pingue