title: Diagnostic efficacy of the leukogram and the chemiluminometric ACTH measurement to diagnose canine hypoadrenocorticism.
abstract: OBJECTIVE
  The gold standard in the diagnosis of canine hypoadrenocorticism (HA) is the adrenocorticotropin (ACTH) response test. As synthetic ACTH (tetracosactide [Synacthen®]) is currently not available in the European Union, the evaluation of other diagnostic tests seemed warranted. The diagnostic efficacy of electrolytes, the leukogram and endogenous ACTH concentrations to diagnose HA was investigated.
  
  
  METHODS
  The medical records of 145 dogs with clinical signs suspect for spontaneous HA were included in a retrospective study. HA was diagnosed (n = 38) or ruled out (n = 84) by using an ACTH response test. In 23 patients HA was excluded by basal cortisol measurement. The diagnostic performance of various variables was assessed based on receiver operating characteristic (ROC) curves and by calculating differential positive rates. A decision tree (IBM SPSS Decision Trees 20, IBM Corporation) was constructed with the variables neutrophil to lymphocyte ratio (N/LR) and sodium to potassium ratio (Na/KR) to illustrate the diagnostic efficacy of the respective test results.
  
  
  RESULTS
  The best single variables to diagnose HA were the endogenous ACTH concentration (area under the ROC curve [ROC AUC] 0.97; cutoff > 50 pmol/l: sensitivity 96%, specificity 100%) and the Na/KR (ROC AUC 0.905; cutoff ≤ 22: sensitivity 92%, specificity 91%). The diagnostic performance of various variables of the leukogram was poor to moderate (ROC AUC 0.625-0.828). 68% of dogs with HA had a Na/KR ≤ 22 and a N/LR ≤ 2.3, a combination not observed in dogs with non-adrenal diseases.
  
  
  CONCLUSIONS
  As secondary HA is very rare, endogenous ACTH measurement is a very good alternative to the traditional ACTH response test. Data also suggest that the combination of a Na/KR ≤ 22 and a N/LR ≤ 2.3 is highly specific and can be used to rule in HA.
authors.affiliation: Dr. Florian K. Zeugswetter, University of Veterinary Medicine Vienna, Department of Companion Animals and Horses, Veterinaerplatz 1, 1210 Vienna, Austria, Email: florian.zeugswetter@vetmeduni.ac.at.
authors.forename: F K
authors.initials: FK
authors.lastname: Zeugswetter
authors.forename: I
authors.initials: I
authors.lastname: Schwendenwein
mesh_terms: D000309:Adrenal Insufficiency / Q000097:blood / Q000175:diagnosis / Q000662:veterinary*; D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000818:Animals; D004283:Dog Diseases / Q000097:blood / Q000175:diagnosis*; D004285:Dogs; D005260:Female; D007958:Leukocyte Count / Q000662:veterinary*; D008163:Luminescent Measurements; D008297:Male; D011188:Potassium / Q000097:blood; D012372:ROC Curve; D012189:Retrospective Studies; D012964:Sodium / Q000097:blood
chemical_list: D000324:Adrenocorticotropic Hormone; D012964:Sodium; D011188:Potassium
keywords: Addison’s disease; White blood cell count; adrenocorticotropin; dog; neutrophil to lymphocyte ratio; sodium to potassium ratio