Open AccessEstimating the Sensitivity and Specificity of Real‐Time Quantitative PCR of Fecal Samples for Diagnosis of Rhodococcus equi Pneumonia in Foals
Author(s) -
Shaw S.D.,
Cohen N.D.,
Chaffin M.K.,
Blodgett G.P.,
Syndergaard M.,
Hurych D.
Publication year - 2015
Publication title -
journal of veterinary internal medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.356
H-Index - 103
eISSN - 1939-1676
pISSN - 0891-6640
DOI - 10.1111/jvim.13631
Subject(s) - feces , rhodococcus equi , pneumonia , medicine , subclinical infection , horse , receiver operating characteristic , veterinary medicine , gastroenterology , microbiology and biotechnology , biology , virulence , paleontology , biochemistry , gene
Background Real‐time, quantitative PCR ( qPCR ) methods for detecting R hodococcus 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. Animals 186 foals born in 2011 at an R . equi ‐endemic ranch in T exas. 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 and Clinical Importance 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.