Correlation of Lawsonia intracellularis semi-quantitative fecal polymerase chain reaction assay results with the presence of histologic lesions of proliferative enteropathy and positive immunohistochemical staining
Eric R. Burrough, DVM, PhD, Diplomate ACVP; Marisa L. Rotolo, DVM; Philip C. Gauger, DVM, PhD; Darin M. Madson, DVM, PhD, Diplomate ACVP; Kent J. Schwartz, DVM, MS
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The presence of Lawsonia intracellularis in swine feces is commonly confirmed using highly sensitive polymerase chain reaction (PCR) assays. The objective of this retrospective study was to determine, on the basis of cycle-threshold (Ct) values for a given real-time PCR assay, the likelihood of positive fecal PCR results correlating with the presence of histologic lesions and positive immunohistochemistry (IHC) in tissues from the same submission. Sixty-three cases submitted from 2012 to 2014 were selected for analysis, with Ct values ranging from 16.94 to 37.66. There was a strong negative correlation between the Ct value of a positive PCR and the quantity of L intracellularis antigen detected by IHC. On the basis of these results, PCR Ct values < 20.00 had a positive predictive value of 100% for the presence of proliferative lesions and L intracellularis antigen by IHC, and PCR Ct values > 30.00 were associated with a negative predictive value of > 95% for these variables. These data reveal a strong association between Ct values and the presence or absence of L intracellularis infection detectible by light microscopy, suggesting that specific ranges of Ct values carry strong predictive value for the presence or absence of porcine proliferative enteropathy.
Keywords: Lawsonia intracellularis, porcine proliferative enteropathy, PPE
Cite as: Burrough ER, Rotolo ML, Gauger PC, et al. Correlation of Lawsonia intracellularis semi-quantitative fecal polymerase chain reaction assay results with the presence of histologic lesions of proliferative enteropathy and positive immunohistochemical staining. J Swine Health Prod 2015;23(4):204-207.
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