A guide to risk assessment in animal care and use programs: the metaphor of the 3-legged stool.

A high-quality contemporary animal care and use program (ACUP) is a multifaceted dynamic system with three distinct organizational entities--the institutional official (IO), attending veterinarian (AV), and institutional animal care and use committee (IACUC)--each of whose authorities and responsibilities are mandated by a complex set of laws, regulations, policies, and guidelines. The 3-legged stool is presented here as a metaphor for the properly constituted and functioning ACUP, with the legs of the stool representing the IO, AV, and IACUC: when one component is weakened, the stool remains standing but tilts--the ACUP remains in compliance with animal welfare standards but is at risk of failure. Mechanisms for assessing an ACUP's strengths and weaknesses include both external evaluators, such as the US Department of Agriculture, Office of Laboratory Animal Welfare, and Association for Assessment and Accreditation of Laboratory Animal Care, and internal evaluators, such as the IACUC, AV, and IO.