Abstract
Feline coronavirus (FCoV) infects both domestic and wild felids and has the potential to cause feline infectious peritonitis (FIP), a progressive and often fatal systemic disease. Although rapid diagnosis and treatment are crucial in cases of FIP, conventional reverse-transcription quantitative real-time PCR (RT-qPCR) requires RNA extraction and specialized equipment, limiting its use for timely testing in general veterinary practice. We evaluated the performance of a direct RT-qPCR method using the PicoGene PCR1100 system (GoFoton, Ibaraki, Japan), which omits the RNA extraction step and delivers results within ~40 min. Compared with FCoV culture supernatants and extracted RNA, we estimated the limit of detection of this direct RT-qPCR method to be 150 copies/reaction-a detection sensitivity equivalent to that of conventional RT-qPCR targeting the FCoV 3'-UTR. We observed no cross-reactivity with other feline viruses or SARS-CoV-2. We subsequently analyzed 28 pleural and abdominal effusions collected from cats suspected of having FIP to compare the direct RT-qPCR method with the conventional approach. The sensitivity of the direct RT-qPCR method was 95.5% (95% CI: [78.2, 99.2]) and the specificity was 100% (95% CI: [61.0, 100.0]), which supports the use of the PCR1100 system as a rapid and user-friendly point-of-care tool for the detection of FCoV RNA in effusion samples.