Help me understand my cat's FIP test results

[dre2xl]

My cat has been tested FIP positive. Because her symptoms have not been consistent with FIP (she has been well for over a week now), the vet gave a 50-50 chance of a false positive.

I saw only one number on her coronavirus titre results, 1:408. Is this high or is this low for a cat that has FIP? I read that a ratio of 1:1280 is needed for a diagnosis. So is this “worse” than 1:1280 or “better”?

[CheekyMonkey613]

From Cornell Feline Health:

A positive test result only means the cat has had a prior exposure to a coronavirus – not necessarily one that causes FIP – and has developed antibodies against that virus. If the test is negative, it means the cat has not been exposed to a coronavirus.

The number, or titer, that is reported is the highest serum dilution that still produced a positive reaction. Low titers indicate a small amount of coronavirus antibodies in the serum, while high titers indicate greater amounts of antibodies. A healthy cat with a high titer is not necessarily more likely to develop FIP or be a carrier of an FIP-causing coronavirus than a cat with a low titer. It also is not necessarily protected against future FIP virus infection.

A presumptive diagnosis of FIP can usually be made on the basis of clinical signs, routine laboratory tests, and evaluation of abdominal or chest fluid. Some cases, however, present a diagnostic challenge, since the signs of illness are not distinct for FIP. In all cases, a tissue biopsy is the only way to absolutely confirm a diagnosis of FIP.

Hope that helps. Good luck with your baby.

[dre2xl]

@CheekyMonkey613

From Cornell Feline Health:
Hope that helps. Good luck with your baby.

Thank you very much for the link… she definitely does not have “wet” FIP. The vet said to wait a month and if she’s still well, then she’s home free.

The page was very informative, but didn’t really answer my question… should’ve phrased it better… Is the titre a ratio, where higher numbers are better, or a count per part, where lower numbers are better? The page would imply that lower numbers are better, but I don’t want to hold any false hope…

[vetbridge]

@dre2xl

Thank you very much for the link… she definitely does not have “wet” FIP. The vet said to wait a month and if she’s still well, then she’s home free.

The page was very informative, but didn’t really answer my question… should’ve phrased it better… Is the titre a ratio, where higher numbers are better, or a count per part, where lower numbers are better? The page would imply that lower numbers are better, but I don’t want to hold any false hope…

I am a veterinarian. IMHO the “FIP titer” is useless.

Generally speaking, a bigger number is worse. The ratio is the dilution at which virus is still able to be demonstrated. So, the “bigger” the number, the more virus is present. However, there are times when actively infected sick cats have a negative titewr due to virus/antibody interaction. Also, a “high titer” can be due to a non pathologic form of corona virus.

Many species have a corona virus which typically cause diarrhea. In the cat “for some reason” corona virus can “transmute” to a more deadly version. Sorry for the vague wording…but that is the way it is.

A diagnosis of Feline Infectious Peritonitis (FIP) is made (again IMHO) using clinical signs, lab work, and often histopathology of tissue. A pyogranulomatous vasculitis is what the pathologist looks for.

HTH

[dre2xl]

vetbridge, thank you for your insight. Shadowfax was vomiting and had a fever last week, but has been well since last Thursday. She does not have diaherrea; on the contrary, she has constipation.

The vet said that she could not really make a diagnosis because if Shadowfax has FIP at all it is “dry” FIP which is apparently much harder to diagnose. Is there any way the diagnosis can be narrowed down in the case of dry FIP?

I guess I’m grasping at straws here looking for a “yes” or “no” answer. Since FIP takes only weeks for it to become fatal, when can I reasonably start believing that she’s home free? One, two, three more weeks>

[vetbridge]

@dre2xl

vetbridge, thank you for your insight. Shadowfax was vomiting and had a fever last week, but has been well since last Thursday. She does not have diaherrea; on the contrary, she has constipation.

The vet said that she could not really make a diagnosis because if Shadowfax has FIP at all it is “dry” FIP which is apparently much harder to diagnose. Is there any way the diagnosis can be narrowed down in the case of dry FIP?

I guess I’m grasping at straws here looking for a “yes” or “no” answer. Since FIP takes only weeks for it to become fatal, when can I reasonably start believing that she’s home free? One, two, three more weeks>

FIP typically causes a fever that is not responsive to antibiotics. Also,in almost all cases there is an increased seum total protein in the form of globulins. Many cases have retinal hemmorhage which is simple to look for. Also, many cats infected with FIP virus also are positive for feline leukemia virus which is simple to test for.

HTH

[dre2xl]

I talked to my vet today (she saw Shadowfax yesterday most recently) and:

1. The vet didn’t see anything abnormal in her eyes.
2. Normal gobulins at 3.34 grams per deciliter
3. Normal lymphocytes at 20%

Her temperature was 104 initially but has since came back down to normal.

So would I be correct in assuming that you’d probably consider this a false positive?

[vetbridge]

@dre2xl

So would I be correct in assuming that you’d probably consider this a false positive?

I think that would be a safe assumption. In fact, a high corona virus titer in and of itself is not really “positive” for anything specific.