Table 1.

Assigning an uncertainty factor.

Uncertainty Factor	Definition	Prospective Severity Classification	Retrospective Assessment
Low	Extensive literature (e.g., scientific articles or databases of genetically altered (GA) animals) or experience with the method or phenotype is available that provides a clear picture of what is expected	Possible	Recommended but not required
Medium	Some literature or experience with the method or phenotype is available that provide indicators for severity assessment, but is still vague	Possible, but vague	Strongly recommended to confirm or revise the prospective severity assessment
High	No literature or experience with the method or phenotype is available	Not possible	Retrospective assessment mandatory