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How is the dry form of FIP diagnosed? - kittyhealth - 02-01-2022
Diagnosing Non-Effusive ("Dry") with ocular and/or neurological involvement FIP
Dry FIP may present with a variety of symptoms, many of which are consistent with other conditions as well, which makes a diagnosis more difficult. Cats with dry FIP often present with lethargy, stunted growth, inappetence, fever, anemia, and/or protruding third eyelid(s). There is often a history of diarrhea.
If there is ocular involvement, uveitis, keratic precipitates - KP (keratic precipitate is an inflammatory cell deposit on the corneal endothelium), aqueous flare, or retinal vessel cuffing may be present.
If the virus has affected the central nervous system or brain, neurological symptoms may include ataxia, tremors, seizures, or nystagmus (darting eyes).
Complete CBC & Chemistry Panel
Whenever dry FIP is suspected, a complete CBC and chemistry panel should be the first step toward a diagnosis. The typical FIP blood work will show low albumin, high globulin, high white blood cell count, low red blood cell count, high neutrophils, high protein, and high bilirubin. Most FIP cats will have non-regenerative anemia, as well as a persistent fever. Not all blood results will look the same; however, if some markers are present and the cat’s symptoms suggest a presumptive diagnosis of FIP, further diagnostics are generally recommended.
However, more and more dry FIP cases are emerging in which the blood count does not show any of the above characteristics, but the symptoms are more than clear.
Ultrasound
Dry FIP causes lesions to whichever organs are affected by the virus. An ultrasound can reveal whether or not lesions are present, as well as check for enlarged mesenteric lymph node(s) and enlarged kidneys. During the ultrasound, a fine needle aspiration of the lesions may be done in the office, and with typically no need for anesthesia. Samples should be sent to a lab for immunostaining.
Immunostaining
Direct staining of FCoVs within macrophages by immunofluorescence in cytocentrifuged effusions or immunohistochemistry in tissue is considered the most specific test to confirm FIP. Immunostaining cannot differentiate between the “harmless” FCoV and FIP-causing FCoV, but finding infected macrophages in characteristic pyogranulomatous lesions or in inflammatory effusions is highly associated with FIP. In a recent study in which a large number of cats with confirmed FIP and controls with other confirmed diseases were investigated, positive immunofluorescence staining of intracellular FCoV antigen in macrophages of the effusion was 100% predictive of FIP. Although immunostaining has a high positive predictive value, the negative predictive value is not high, which means that a positive result is likely to be a true positive, while a negative result may not be a true negative. Therefore, a negative result does not rule out a diagnosis of FIP.
GS As A Diagnostic
In cases where FIP is the presumptive diagnosis, an alternative to extensive additional lab work or procedures is to use GS diagnostically. GS441 does not treat or cure any condition other than FIP therefore, if the cat begins to respond after a few doses, FIP can be confirmed. If the cat does not have FIP, the GS will do no harm.