title: Use of antibody titers measured via serum synergistic hemolysis inhibition testing to predict internal Corynebacterium pseudotuberculosis infection in horses.
abstract: OBJECTIVE
  To estimate likelihood ratios (LRs) of correctly identifying internal Corynebacterium pseudotuberculosis infection in horses by measurement of antibody titers via serum synergistic hemolysis inhibition (SHI) testing.
  
  
  METHODS
  Retrospective case-control study.
  
  
  METHODS
  170 horses (171 records; 92 cases of C pseudotuberculosis infection and 79 controls).
  
  
  METHODS
  Medical records were reviewed, and horses were grouped on the basis of evidence of internal or external C pseudotuberculosis infection. The LRs and 95% confidence intervals for identification of internal C pseudotuberculosis infection by use of SHI test results were estimated.
  
  
  RESULTS
  LRs for C pseudotuberculosis infection increased as antibody titers increased when all horses were included in analyses; LRs for detecting internal infection were significantly > 1 (null value) for reciprocal antibody titers ≥ 1,280 overall and > 160 when horses with external abscesses were excluded. Likelihood ratios for detecting internal infection did not differ from 1 (indicating no change in pretest-to-posttest odds of internal infection) when only horses with external C pseudotuberculosis infection (horses with external and internal abscesses vs those with external abscesses only) were included. The LR for detecting internal infection was 2.98 (95% confidence interval, 2.19 to 4.05) for horses with titers ≥ 512.
  
  
  CONCLUSIONS
  In the study population, higher titers were typically more indicative of active external or internal C pseudotuberculosis infection than of internal disease specifically. The SHI test was not a useful predictor of internal C pseudotuberculosis infection in horses with external abscesses but was useful in the absence of external disease.
authors.affiliation: Department of Medicine, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Jeske
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Spier
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Whitcomb
authors.forename: Nicola
authors.initials: N
authors.lastname: Pusterla
authors.forename: Ian A
authors.initials: IA
authors.lastname: Gardner
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D016022:Case-Control Studies; D003354:Corynebacterium Infections / Q000097:blood / Q000175:diagnosis / Q000276:immunology / Q000662:veterinary*; D016925:Corynebacterium pseudotuberculosis; D005260:Female; D006734:Horse Diseases / Q000097:blood* / Q000276:immunology / Q000382:microbiology; D006736:Horses; D008297:Male; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D000907:Antibodies, Bacterial