Diagnosis of Feline Infectious Peritonitis: A Review of the Current Literature

Abstract

Feline infectious peritonitis (FIP) is a fatal disease that poses several challenges for veterinarians: clinical signs and laboratory changes are non-specific, and there are two pathotypes of the etiologic agent feline coronavirus (FCoV), sometimes referred to as feline enteric coronavirus (FECV) and feline infectious peritonitis virus (FIPV) that vary fundamentally in their virulence, but are indistinguishable by a number of diagnostic methods. This review focuses on all important steps every veterinary practitioner has to deal with and new diagnostic tests that can be considered when encountering a cat with suspected FIP with the aim to establish a definitive diagnosis. It gives an overview on all available direct and indirect diagnostic tests and their sensitivity and specificity reported in the literature in different sample material. By providing summarized data for sensitivity and specificity of each diagnostic test and each sample material, which can easily be accessed in tables, this review can help to facilitate the interpretation of different diagnostic tests and raise awareness of their advantages and limitations. Additionally, diagnostic trees depict recommended diagnostic steps that should be performed in cats suspected of having FIP based on their clinical signs or clinicopathologic abnormalities. These steps can easily be followed in clinical practice.

Keywords: FIP; ICC; IHC; RT-PCR; antibody; diagnosis; immunocytochemistry; immunohistochemistry.

Figure 1

Decision trees depicting recommended diagnostic steps in a case suspicious of FIP, depending on a cat’s clinical presentation: (a) diagnostic steps recommended in a cat presenting with effusion; (b) diagnostic steps recommended in a cat presenting with neurological signs; (c) diagnostic steps recommended in a cat presenting with uveitis; (d) diagnostic steps recommended in a cat presenting with non-specific clinical signs. CSF = cerebrospinal fluid; FCoV = feline coronavirus; FIP = feline infectious peritonitis; FNA = fine-needle aspirates; IHC = immunohistochemistry; RT-PCR = reverse transcriptase polymerase chain reaction; S gene = spike gene.