title: Evaluation of the Cortisol-to-ACTH Ratio in Dogs with Hypoadrenocorticism, Dogs with Diseases Mimicking Hypoadrenocorticism and in Healthy Dogs.
abstract: BACKGROUND
  The adrenocorticotropic hormone (ACTH) stimulation test is the gold standard for diagnosing hypoadrenocorticism (HA) in dogs. However, problems with the availability of synthetic ACTH (tetracosactrin/cosyntropin) and increased costs have prompted the need for alternative methods.
  
  
  OBJECTIVE
  To prospectively evaluate the cortisol-to-ACTH ratio (CAR) as a screening test for diagnosing canine HA.
  
  
  METHODS
  Twenty three dogs with newly diagnosed HA; 79 dogs with diseases mimicking HA; 30 healthy dogs.
  
  
  METHODS
  Plasma ACTH and baseline cortisol concentrations were measured before i.v. administration of 5 μg/kg ACTH in all dogs. CAR was calculated and the diagnostic performance of ACTH, baseline cortisol, CAR and sodium-to-potassium ratios (SPRs) was assessed based on receiver operating characteristics (ROC) curves calculating the area under the ROC curve.
  
  
  RESULTS
  The CAR was significantly lower in dogs with HA compared to that in healthy dogs and in those with diseases mimicking HA (P < .0001). There was an overlap between HA dogs and those with HA mimicking diseases, but CAR still was the best parameter for diagnosing HA (ROC AUC 0.998), followed by the ACTH concentration (ROC AUC 0.97), baseline cortisol concentration (ROC AUC 0.96), and SPR (ROC AUC 0.86). With a CAR of >0.01 the diagnostic sensitivity and specificity were 100% and 99%, respectively.
  
  
  CONCLUSIONS
  Calculation of the CAR is a useful screening test for diagnosing primary HA. As a consequence of the observed overlap between the groups, however, misdiagnosis cannot be completely excluded. Moreover, additional studies are needed to evaluate the diagnostic reliability of CAR in more dogs with secondary HA.
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: F S
authors.initials: FS
authors.lastname: Boretti
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: F
authors.initials: F
authors.lastname: Meyer
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: W A
authors.initials: WA
authors.lastname: Burkhardt
authors.affiliation: Clinical Laboratory, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Riond
authors.affiliation: Clinical Laboratory, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Hofmann-Lehmann
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: C E
authors.initials: CE
authors.lastname: Reusch
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: N S
authors.initials: NS
authors.lastname: Sieber-Ruckstuhl
mesh_terms: D000309:Adrenal Insufficiency / Q000097:blood / Q000175:diagnosis / Q000662:veterinary*; D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000818:Animals; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D003937:Diagnosis, Differential; D004283:Dog Diseases / Q000097:blood / Q000175:diagnosis*; D004285:Dogs; D005260:Female; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D011188:Potassium / Q000097:blood; D011446:Prospective Studies; D012964:Sodium / Q000097:blood
chemical_list: D015415:Biomarkers; D000324:Adrenocorticotropic Hormone; D012964:Sodium; D011188:Potassium; D006854:Hydrocortisone
keywords: Adrenal insufficiency; Adrenocorticotropic; Canine; Cosyntropin; Hormone