title: Evaluation of Four Diagnostic Tests for Insulin Dysregulation in Adult Light-Breed Horses.
abstract: BACKGROUND
  Several tests have been evaluated in horses for quantifying insulin dysregulation to support a diagnosis of equine metabolic syndrome. Comparing the performance of these tests in the same horses will provide clarification of their accuracy in the diagnosis of equine insulin dysregulation.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the agreement between basal serum insulin concentrations (BIC), the oral sugar test (OST), the combined glucose-insulin test (CGIT), and the frequently sampled insulin-modified intravenous glucose tolerance test (FSIGTT).
  
  
  METHODS
  Twelve healthy, light-breed horses.
  
  
  METHODS
  Randomized, prospective study. Each of the above tests was performed on 12 horses.
  
  
  RESULTS
  Minimal model analysis of the FSIGTT was considered the reference standard and classified 7 horses as insulin resistant (IR) and 5 as insulin sensitive (IS). In contrast, BIC and OST assessment using conventional cut-off values classified all horses as IS. Kappa coefficients, measuring agreement among BIC, OST, CGIT, and FSIGTT were poor to fair. Sensitivity of the CGIT (positive phase duration of the glucose curve >45 minutes) was 85.7% and specificity was 40%, whereas CGIT ([insulin]45 >100 μIU/mL) sensitivity and specificity were 28.5% and 100%, respectively. Area under the glucose curve (AUCg0-120 ) was significantly correlated among the OST, CGIT, and FSIGTT, but Bland-Altman method and Lin's concordance coefficient showed a lack of agreement.
  
  
  CONCLUSIONS
  Current criteria for diagnosis of insulin resistance using BIC and the OST are highly specific but lack sensitivity. The CGIT displayed better sensitivity and specificity, but modifications may be necessary to improve agreement with minimal model analysis.
authors.affiliation: Ohio State University College of Veterinary Medicine, Columbus, OH.
authors.forename: L K
authors.initials: LK
authors.lastname: Dunbar
authors.affiliation: Ohio State University College of Veterinary Medicine, Columbus, OH.
authors.forename: K A
authors.initials: KA
authors.lastname: Mielnicki
authors.affiliation: Ohio State University College of Veterinary Medicine, Columbus, OH.
authors.forename: K A
authors.initials: KA
authors.lastname: Dembek
authors.affiliation: Ohio State University College of Veterinary Medicine, Columbus, OH.
authors.forename: R E
authors.initials: RE
authors.lastname: Toribio
authors.affiliation: Ohio State University College of Veterinary Medicine, Columbus, OH.
authors.forename: T A
authors.initials: TA
authors.lastname: Burns
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis*; D005260:Female; D005951:Glucose Tolerance Test / Q000662:veterinary; D006734:Horse Diseases / Q000175:diagnosis* / Q000378:metabolism; D006736:Horses; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance; D008297:Male; D011446:Prospective Studies; D012680:Sensitivity and Specificity
chemical_list: D001786:Blood Glucose; D007328:Insulin
keywords: Equine metabolic syndrome; Insulin dysregulation; Laminitis