Utility of feline coronavirus antibody tests

Abstract

Eight different tests for antibodies to feline coronavirus (FCoV) were evaluated for attributes that are important in situations in veterinary practice. We compared four indirect immunofluorescent antibody tests (IFAT), one enzyme-linked immunosorbent assay (ELISA) (FCoV Immunocomb; Biogal) and three rapid immunochromatographic (RIM) tests against a panel of samples designated by consensus as positive or negative. Specificity was 100% for all but the two IFATs based on transmissible gastroenteritis virus (TGEV), at 83.3% and 97.5%. The IFAT and ELISA tests were best for obtaining an antibody titre and for working in the presence of virus. The RIM tests were the best for obtaining a result quickly (10-15 mins); of these, the Speed F-Corona was the most sensitive, at 92.4%, followed by FASTest feline infectious peritonitis (FIP; 84.6%) and Anigen Rapid FCoV antibody test (64.1%). Sensitivity was 100% for the ELISA, one FCoV IFAT and one TGEV IFAT; and 98.2% for a second TGEV IFA and 96.1% for a second FCoV IFAT. All tests worked with effusions, even when only blood products were stipulated in the instruction manual. The ELISA and Anigen RIM tests were best for small quantities of sample. The most appropriate FCoV antibody test to use depends on the reason for testing: in excluding a diagnosis of FIP, sensitivity, specificity, small sample quantity, rapidity and ability to work in the presence of virus all matter. For FCoV screening, speed and sensitivity are important, and for FCoV elimination antibody titre is essential.

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

“…These 21 samples with conflicting results are likely to be true positive since an IIF-negative result could be related to antibody sequestration by high viral loads (Meli et al, 2013). In addition, Addie et al (2015) demonstrated that up to 43% antibodypositive effusions from FIP cases were negative for FCoV RNA, likely as a consequence of PCR inhibition by interfering substances or RNA degradation during sample transportation and storage. However, in the absence of alternative diagnosis, even those 5 cats with neither FCoV antibodies nor RNA in their effusions could not be definitively considered as non-FIP animals (Addie et al, 2015).…”

“…In addition, Addie et al (2015) demonstrated that up to 43% antibodypositive effusions from FIP cases were negative for FCoV RNA, likely as a consequence of PCR inhibition by interfering substances or RNA degradation during sample transportation and storage. However, in the absence of alternative diagnosis, even those 5 cats with neither FCoV antibodies nor RNA in their effusions could not be definitively considered as non-FIP animals (Addie et al, 2015). Unfortunately, clinical cases were mostly untraceable and confirmatory necropsy was not done in any case, so that the lack of confirmatory testing represents the main limitation of the present study.…”

Polyprenyl Immunostimulant Treatment of Cats with Presumptive Non-Effusive Feline Infectious Peritonitis In a Field Study

“…The antibody titers were tested by IFA in 49 cats and, on the scale proposed by Addie et al ( 17 ), were ranked from high positive (400–1,280; n = 13) to very high positive (>1,280, n = 36); 10 of the 49 had titers > 12,800. In the two cats with low positive titers (100), the diagnosis was confirmed by immunostaining of biopsied lesions for the FCoV antigen.…”

Feline infectious peritonitis: answers to frequently asked questions concerning FIP and coronavirus

“…One quick way to establish whether that was possible is to look at the incubation period: from first becoming infected with FCoV to the development of FIP takes at least 3 weeks, so if a cat has been spayed, then is noticed to have an effusion a week later when the stitches are being removed, she must have been already infected prior to the operation. (Addie, Le Poder, et al, 2015). Because many pedigree kittens will have antibodies to FCoV, if may be preferable to offer a pre-operation RT-PCR test to establish if a cat is actually shedding FCoV.…”