title: Evaluation of Basal Serum or Plasma Cortisol Concentrations for the Diagnosis of Hypoadrenocorticism in Dogs.
abstract: BACKGROUND
  Previous studies that included limited numbers of affected dogs have suggested basal cortisol concentrations ≤55 nmol/L (2 μg/dL) are sensitive, but nonspecific, for a diagnosis of hypoadrenocorticism. A detailed assessment of the diagnostic utility of basal cortisol concentrations is warranted.
  
  
  OBJECTIVE
  To evaluate the utility of basal cortisol concentrations for the diagnosis of hypoadrenocorticism in a large number of dogs, including those with and without serum electrolyte abnormalities.
  
  
  METHODS
  Five hundred and twenty-two dogs, including 163 dogs with hypoadrenocorticism, 351 dogs with nonadrenal gland illness, and 8 dogs with equivocal results.
  
  
  METHODS
  Retrospective study. Basal and post-ACTH cortisol concentrations and sodium and potassium concentrations were collected from medical records. A receiver operating characteristic (ROC) curve was constructed for basal cortisol concentrations by standard methodologies. Sensitivity, specificity, and predictive values were determined for various cut-points.
  
  
  RESULTS
  The area under the ROC curve was 0.988 and was similarly excellent regardless of serum electrolyte concentrations. At the most discriminatory cut-point of 22 nmol/L (0.8 μg/dL), sensitivity and specificity were 96.9 and 95.7%, respectively. A basal cortisol concentration of ≤55 nmol/L (2 μg/dL) resulted in a sensitivity of 99.4%. Conversely, a basal cortisol concentration of ≤5.5 nmol/L (0.19 μg/dL) resulted in a specificity of 99.1%.
  
  
  CONCLUSIONS
  Similar to findings in previous studies, basal cortisol concentrations >55 nmol/L (2 μg/dL) are useful in excluding a diagnosis of hypoadrenocorticism. Interestingly, excellent specificities and positive predictive values were observed at lower cut-point cortisol concentrations.
authors.affiliation: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI.
authors.forename: A J
authors.initials: AJ
authors.lastname: Gold
authors.affiliation: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI.
authors.forename: D K
authors.initials: DK
authors.lastname: Langlois
authors.affiliation: and the Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI.
authors.forename: K R
authors.initials: KR
authors.lastname: Refsal
mesh_terms: D000309:Adrenal Insufficiency / Q000097:blood / Q000175:diagnosis / Q000662:veterinary*; D000818:Animals; D004283:Dog Diseases / Q000097:blood* / Q000175:diagnosis; D004285:Dogs; D006854:Hydrocortisone / Q000097:blood*; D011188:Potassium / Q000097:blood; D012189:Retrospective Studies; D012964:Sodium / Q000097:blood
chemical_list: D012964:Sodium; D011188:Potassium; D006854:Hydrocortisone
keywords: ACTH; Addison's disease; Adrenal gland; Endocrinology