One day after internal medicine specialists at Health Center Associates notified West Penn Allegheny they were leaving the hospital system to join the University of Pittsburgh Medical Center on Dec. 1, two West Penn administrators walked into the group's Bloomfield offices and ordered the doctors to leave the premises that day. The incident this week underscores the ongoing intense competition between the two health systems. Earlier this year, a group of six obstetrics/gynecology physicians at UPMC Mercy were locked out of their offices one month after giving notice that they were moving to West Penn Hospital.