The veterinarian must look for clinical signs of the disease by taking a thorough history, performing a complete physical examination of the cat, and taking blood tests that detect abnormalities in body organs, such as the kidney or liver.
For cats that have symptoms of effusive FIP, an important diagnostic procedure requires taking a sample of the fluid that is building up within the cat's abdomen and submitting this for analysis of the cell types and protein content present within the fluid. For cats that show signs of the dry form of the disease, an organ biopsy of the kidneys and lymph nodes can be taken and sent to a pathologist to look for the microscopic changes that occur in cats with FIP. This procedure is not always recommended, however, as it creates stress that can worsen a sick cat's condition.
At this time, there are no specific diagnostic tests short of autopsy that can determine definitively whether a cat has FIP. The blood tests that are available simply determine if the cat has been exposed to the coronavirus. Exposure to the coronavirus, however, does not mean necessarily that the animal has FIP; typically, the coronavirus leads to other minor disorders, such as intestinal problems like diarrhea and vomiting.
Serologic testing for exposure to feline coronavirus may be conducted if the clinical signs of FIP are suggestive of the disease and confirmation of exposure is needed. An owner may need such a confirmation to ensure that a pet is not transmitting the disease to other animals. Breeding facilities also may request such testing to determine whether there is a danger of spreading the coronavirus to other cats.
