title: Estimating the Sensitivity and Specificity of Real-Time Quantitative PCR of Fecal Samples for Diagnosis of Rhodococcus equi Pneumonia in Foals.
abstract: BACKGROUND
  Real-time, quantitative PCR (qPCR) methods for detecting Rhodococcus equi in feces have been developed as a noninvasive, rapid diagnostic test for R. equi pneumonia, but have not been evaluated in a large population of foals.
  
  
  OBJECTIVE
  The objective of this study was to evaluate the clinical utility of fecal PCR as a diagnostic test for R. equi pneumonia in foals using receiver operating characteristic (ROC) methods.
  
  
  METHODS
  186 foals born in 2011 at an R. equi-endemic ranch in Texas.
  
  
  METHODS
  Fecal samples were collected at the time of onset of clinical signs for pneumonic foals (n = 31). Foals with pneumonia were matched by age and birth date to healthy (n = 31) and subclinical (n = 124) control foals; fecal samples were collected from these controls. DNA was extracted from feces using commercial kits and concentration of virulent R. equi in feces was determined by qPCR.
  
  
  RESULTS
  Concentration of R. equi in feces differed significantly (P < .05) among groups. The area under the ROC curve for fecal qPCR for diagnosis of R. equi pneumonia was 89% (95% CI, 83-99), with a sensitivity of 94% and specificity of 72%.
  
  
  CONCLUSIONS
  qPCR of feces can be useful as an alternative to tracheobronchial aspiration for the diagnosis of R. equi in foals with clinical signs of pneumonia. Caution should be used in extrapolating results of this study to other populations because fecal concentration of R. equi might vary by geographic location or management practices.
authors.affiliation: Department of Large Animal Clinical Sciences, College of Biomedical Sciences and Veterinary Medicine, Texas A&M University, College Station, TX.
authors.forename: S D
authors.initials: SD
authors.lastname: Shaw
authors.affiliation: Department of Large Animal Clinical Sciences, College of Biomedical Sciences and Veterinary Medicine, Texas A&M University, College Station, TX.
authors.forename: N D
authors.initials: ND
authors.lastname: Cohen
authors.affiliation: Department of Large Animal Clinical Sciences, College of Biomedical Sciences and Veterinary Medicine, Texas A&M University, College Station, TX.
authors.forename: M K
authors.initials: MK
authors.lastname: Chaffin
authors.affiliation: 6666 Ranch, Guthrie, TX.
authors.forename: G P
authors.initials: GP
authors.lastname: Blodgett
authors.affiliation: 6666 Ranch, Guthrie, TX.
authors.forename: M
authors.initials: M
authors.lastname: Syndergaard
authors.affiliation: Department of Large Animal Clinical Sciences, College of Biomedical Sciences and Veterinary Medicine, Texas A&M University, College Station, TX.
authors.forename: D
authors.initials: D
authors.lastname: Hurych
mesh_terms: D000193:Actinomycetales Infections / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D000818:Animals; D005243:Feces / Q000382:microbiology*; D006734:Horse Diseases / Q000175:diagnosis* / Q000382:microbiology; D006736:Horses; D018410:Pneumonia, Bacterial / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary; D060888:Real-Time Polymerase Chain Reaction; D016929:Rhodococcus equi / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D013781:Texas / Q000453:epidemiology
keywords: Coprologic diagnosis; Horse; Infectious diseases; Pneumonia; Rhodococcus