A comparison between immunofluorescence staining on smears from Membrana nictitans (M3 test), immunohistopathology and routine pathology in cats with suspected feline infectious peritonitis (FIP).

An indirect immunofluorescence method using smears from membrana nictitans (M3 test) to diagnose feline corona virus (FCV) infection was compared with immunohistopathology (using indirect immunofluorescence assay (IFFA) performed on organs (IFO], and routine pathology (RP) in cats with suspected feline infectious peritonitis (FIP). A close correlation between the 2 immunofluorescence methods (IFO and M3) was observed. Although the M3 test requires samples from only 1 organ per animal, both the sensitivity and specificity were high (80%), when compared to IFO (using samples from an average of 5 organs per animal). In 21% of the cats with suspected FIP typical pathological lesions were found. As the M3 test is relatively easy to perform, it could reduce work-load of pathology laboratories and provide valuable data for clinical and epidemiological use.