Use of basal serum or plasma cortisol concentrations to rule out a diagnosis of hypoadrenocorticism in dogs: 123 cases (2000-2005).

OBJECTIVE: To determine whether basal serum or plasma cortisol concentration can be used as a screening test to rule out hypoadrenocorticism in dogs. DESIGN: Retrospective case-control study. ANIMALS: 110 dogs with nonadrenal gland illnesses and 13 dogs with hypoadrenocorticism. PROCEDURES: Sensitivity and specificity of basal serum or plasma cortisol concentrations of either 2 microg/dL that are not receiving corticosteroids, mitotane, or ketoconazole are highly unlikely to have hypoadrenocorticism. However, if the basal cortisol concentration is