The Laboratory Response Network (LRN) is a collaborative effort within the US federal government involving the Association of Public Health Laboratories and the Centers for Disease Control and Prevention (CDC). Most state public health laboratories participate as reference laboratories (formerly level B/C) of the LRN. These facilities support hundreds of sentinel (formerly level A) laboratories in local hospitals throughout the United States and can provide sophisticated confirmatory diagnosis and typing of biological agents that may be used in a bioterrorist attack or other bio-agent incident. The LRN was established in 1999. The Laboratory Response Network (LRN) is a collaborative effort within the US federal government involving the Association of Public Health Laboratories and the Centers for Disease Control and Prevention (CDC). Most state public health laboratories participate as reference laboratories (formerly level B/C) of the LRN. These facilities support hundreds of sentinel (formerly level A) laboratories in local hospitals throughout the United States and can provide sophisticated confirmatory diagnosis and typing of biological agents that may be used in a bioterrorist attack or other bio-agent incident. The LRN was established in 1999. The LRN consists of a loose network of government labs at three levels: