Feline coronavirus (FCoV) infection is common; most cats are subclinically affected, but up to 10% develop FIP. Infected cats mount an immune response with detectable antibody levels that decline or may disappear if the cat recovers.
Desirable qualities in an FCoV test include high sensitivity; high specificity; a small sample-size requirement; fast results; ability to determine antibody titer; ability to use effusion in addition to blood, plasma, or serum; and the sensitivity of the test in the presence of virus. A large amount of virus in a sample can reduce or block antibody detection in samples. This study compared 8 FCoV antibody tests for these traits. Four indirect immunofluorescent antibody tests (IFATs), 1 enzyme-linked immunosorbent assay (ELISA), and 3 rapid immunochromatographic (RIM) tests were run on positive (n = 101) and negative (n = 126) samples.
ELISA and RIM tests are available for in-house use. IFATs use cells infected with either FCoV or porcine transmissible gastroenteritis virus (TGEV). Specificity was 100% for all tests except the 2 TGEV IFATs, which were 83.3% and 97.5% specific. Sensitivity was 100% for the ELISA test, 1 TGEV IFAT, and 1 FCoV IFAT; sensitivity for the remaining tests ranged from 64.1% to 98.2%. IFAT and ELISA tests were best for obtaining antibody titers and for samples with virus present. RIM tests provided the fastest results. All tests worked well with effusions. ELISA and 1 RIM test worked best with small sample quantity. FCoV antibody test choice should depend on the goal of testing.