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

Table 4 Results of FCoV antigen immunohistochemistry and FCoV RT-qPCR for tissue from cats with FIP and cats without FIP

Tissue source	RT-qPCR	Immunohistochemistry		Total
Tissue source	RT-qPCR	Negative^a	Positive	Total
Cats with FIP
	Negative	16	7	23
	Positive (relative copy number: median, range)	69 (1.2 × 10³, 1.4 × 10⁷ to 1.6)	132 (4.9 × 10⁴, 1.2 × 10⁸ to 1.2)	201
	Total	85	139	224
Cats without FIP
	Negative	162	0	162
	Positive (relative copy number: median, range)	19 (16, 9.4 × 10³ to 2.7)	0	19
	Total	181	0	181

^aThis includes 11 tissue samples with histopathological changes consistent with FIP, from cats definitively diagnosed with FIP based on analysis of additional tissue, but for which immunohistochemistry was negative (10 were positive for FCoV by RT-qPCR).

ISSN: 1297-9716