Comparison of real-time reverse transcriptase polymerase chain reaction of peripheral blood mononuclear cells, serum and cell-free body cavity effusion for the diagnosis of feline infectious peritonitis

Abstract

Objectives Diagnosis of feline infectious peritonitis (FIP) remains challenging, especially in cats without effusions. The objective of this study was to evaluate the sensitivity and specificity of a real-time reverse transcriptase polymerase chain reaction (RT-PCR) detecting feline coronavirus (FCoV) RNA in peripheral blood mononuclear cells (PBMCs) and serum in comparison with the same real-time RT-PCR in cell-free body cavity effusion. Methods This prospective case-control study included 92 cats. Forty-three cats had a definitive diagnosis of FIP, established either by histopathological examination (n = 28) or by positive immunofluorescence staining of FCoV antigen in macrophages of effusions (n = 11), or by both methods (n = 4). Forty-nine control cats had other diseases but similar clinical signs. Real-time RT-PCR was performed on PBMCs of 37 cats (21 cats with FIP, 16 controls), on serum of 51 cats (26 cats with FIP, 25 controls) and on cell-free body cavity effusion of 69 cats (36 cats with FIP, 33 controls). Sensitivity, specificity, positive and negative predictive value, including 95% confidence intervals (CI), were calculated. Results Real-time RT-PCR of PBMCs, serum and cell-free body cavity effusion showed a specificity of 100% (95% CI 79.4-100% in PBMCs, 86.3-100% in serum, 89.4-100% in cell-free body cavity effusion) and a sensitivity of 28.6% (95% CI 11.3-52.2%) in PBMCs, 15.4% (95% CI 4.4-34.9%) in serum and 88.9% (95% CI 73.9-96.9%) in cell-free body cavity effusion to diagnose FIP. Conclusions and relevance Although it is known that RT-PCR can often provide false-positive results in healthy cats, this real-time RT-PCR was shown to be a specific tool for the diagnosis of FIP when applied in a clinical setting. Sensitivity in cell-free body cavity effusion was high but low in PBMCs and serum. PBMC samples showed a higher sensitivity than serum samples, and are therefore a better choice if no effusion is present.

Limitations of using feline coronavirus spike protein gene mutations to diagnose feline infectious peritonitis

“…This is a marked increase in the number of samples analysed as compared to most previous studies [20,21,29,30], and contains similar numbers of effusion samples to two previous studies [19,31]. Some studies have examined the use of FCoV RT-PCR alone in the diagnosis of FIP using fluid samples [29,31]. Other studies [19,21] compared FCoV RT-PCR to FCoV RT-PCR in combination with characterisation of S gene mutations in the diagnosis of FIP using body cavity fluids, these derived similar sensitivity (72 to 85% for FCoV RT-PCR alone and 60 to 64% for FCoV RT-PCR and S gene mutations characterisation) and specificity (100% for both FCoV RT-PCR alone and FCoV RT-PCR and S gene mutations characterisation) as obtained in this study (sensitivity 78.4% for FCoV RT-PCR alone and 60% FCoV RT-PCR and S gene mutations characterisation; specificity 97.9 and 97.9% respectively).…”

“…In total, 699 tissue, fluid and faeces samples were analysed from 102 cats, 57 with FIP and 45 without FIP. This is a marked increase in the number of samples analysed as compared to most previous studies [20,21,29,30], and contains similar numbers of effusion samples to two previous studies [19,31]. Some studies have examined the use of FCoV RT-PCR alone in the diagnosis of FIP using fluid samples [29,31].…”

Discrepancies between feline coronavirus antibody and nucleic acid detection in effusions of cats with suspected feline infectious peritonitis

“…Molecular methods have been used for detection of FCoV RNA in the effusions of cats with suspected FIP (Gut et al, 1999;Simons et al, 2004;Hornyák et al, 2012;Soma et al, 2013;Doenges et al, 2017;Felten et al, 2017;Longstaff et al, 2017). However, these methods display similar issues related to the diagnostic performances (lack of sensitivity and specificity).…”

Reverse transcriptase loop-mediated isothermal amplification for the detection of feline coronavirus

“…The FCoV is faecally-orally transmitted, worldwide distributed and highly prevalent in feline populations (Addie et al, 2009). Since most of the molecular and serological tools available up to date are not able to distinguish between the not mutated and the mutated pathogenic form of the FCoV, the use of reverse transcriptase polymerase chain reaction (RT-PCR) for the diagnosis of FIP is still extensively discussed Doenges et al, 2016;Felten et al, 2015;Longstaff et al, 2015). On the other hand, PCR is an extremely useful tool for the diagnosis of FCoV infection and shedding and consequently for the identification of shedders, when performed on faeces (Pedersen, 2014).…”