If your cat is presenting multiple symptoms of calicivirus, it’s likely your vet will presume a positive diagnosis and begin treatment. Obtaining a more definitive diagnosis requires more intensive testing. This may involve sampling your cat’s discharge for polymerase chain reaction tests, viral isolation, or immune-histochemical staining. Sometimes, the virus can spread to a cat’s lungs, in which case your vet may recommend a transtracheal wash to obtain additional samples. Your vet might also run X-ray and blood tests to rule out other potential causes of your cat’s symptoms.