title: Investigation into the utility of an immunocytochemical assay in body cavity effusions for diagnosis of feline infectious peritonitis.
abstract: Objectives Feline coronaviruses (FCoVs) exist as two biotypes, feline enteric coronavirus and feline infectious peritonitis virus. Although feline infectious peritonitis (FIP) is a very common disease, the ante-mortem diagnosis of this disease still remains a challenge. Immunofluorescence staining of FCoV in macrophages in effusion has been considered as the reference standard for the diagnosis, but recently this method has been shown to have lower specificity than previously reported. In addition, this method is not widely available and requires the use of fluorescence microscopes. Therefore, it was the aim of this study to evaluate the diagnostic potential of an immunocytochemical (ICC) assay using body cavity effusion. Methods Effusion samples from 27 cats with immunohistochemically confirmed FIP and 29 cats with suspected FIP but a definitive diagnosis of another disease were examined. ICC specimens were evaluated with respect to positive immunostaining. In addition, effusion samples were stained with haematoxylin and eosin and evaluated cytologically. Results A diagnostic sensitivity of 85.2% was recorded for effusion specimens (95% confidence interval [CI] 66.3-95.8), while the diagnostic specificity was only 72.4% (95% CI 52.8-87.3). Conclusions and relevance Once the clinical disease of FIP develops in a cat, it always leads to death, and most of the cats are euthanased within a few days or weeks. As false-positive results might lead to euthanasia of cats suffering from potentially treatable diseases, the diagnostic specificity of a diagnostic tool is the most important factor in a fatal disease like FIP. Thus, the diagnostic utility of this test proved to be insufficient and positive ICC results should be interpreted with caution. Nevertheless, full-body necropsy could not be performed in 13/29 control cats. It is possible that these cats actually suffered from early-stage FIP and that this fact might have influenced the diagnostic specificity of the ICC. Based on the results of the present study, however, ICC of effusion samples currently cannot be recommended to confirm a suspicion of FIP.
authors.affiliation: 1 Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Felten
authors.affiliation: 2 Section of Clinical and Comparative Neuropathology, Institute of Veterinary Pathology, Centre for Clinical Veterinary Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Kaspar
authors.initials: K
authors.lastname: Matiasek
authors.affiliation: 1 Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Gruendl
authors.affiliation: 1 Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Laura
authors.initials: L
authors.lastname: Sangl
authors.affiliation: 1 Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wess
authors.affiliation: 1 Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Hartmann
mesh_terms: D000818:Animals; D002415:Cats; D016765:Coronavirus, Feline / Q000276:immunology / Q000302:isolation & purification*; D016766:Feline Infectious Peritonitis / Q000097:blood / Q000175:diagnosis*; D007150:Immunohistochemistry / Q000662:veterinary; D011446:Prospective Studies; D012680:Sensitivity and Specificity