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

Barker, Emily N.; Stranieri, Angelica; Helps, Chris R.; Porter, Emily L.; Davidson, Andrew D.; Day, Michael J.; Knowles, Toby; Kipar, Anja; Tasker, Séverine

Other study limitations include lack of cytological data for fluid samples, which cannot be performed retrospectively on stored samples, and was not consistently performed at the time of collection due to lack of clinical justification in euthanased cats. However, a number of other studies have examined the use of immunocytochemistry on fluid in the diagnosis of FIP [30, 39] , and reported similar sensitivities for the diagnosis of FIP to the FCoV RT-qPCR used in this study, but observed increased false positive results resulting in reduced specificities. However, in our experience, false positive results are not a relevant issue, provided sufficient cell numbers can be examined; this can be achieved when cells are concentrated in cytospins or when fluids are used to prepare formalin-fixed, paraffin embedded cell pellets that can then be treated like a tissue specimen for IHC (unpublished observations; Anja Kipar) [5] . In addition, pyrosequencing was only used to target a small region of the serotype 1 FCoV genome.