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Ask Dr. Michael Salkin Your Own Question
Dr. Michael Salkin
Dr. Michael Salkin, Veterinarian
Category: Cat
Satisfied Customers: 26138
Experience:  University of California at Davis graduate veterinarian with 44 years of experience
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I tried calling Antech to get an answer to why these tests

Customer Question

I tried calling Antech to get an answer to why these tests differ and of course the vet would not talk to me. These blood tests were taken two weeks apart. Clearly they must be testing a different way. Any way you can find out how/ what u c davis tests so we can try to get a clear answer about this poor isolated cat who hopes antech is correct. Thanks.
Submitted: 5 months ago.
Category: Cat
Expert:  Dr. Michael Salkin replied 5 months ago.

You're speaking to Dr. Michael Salkin. Welcome to JustAnswer. I'm currently typing up my reply.

Expert:  Dr. Michael Salkin replied 5 months ago.

Antech's IgG shows a titer resulting from natural infection or vaccination. Confirmation of infection would involve seeing a 4-fold increase in that titer within 2-3 weeks.

UC Dvis is testing for something different - perhaps antibodies against the 7b protein which is theorized to play a role in FIP disease development. It's thought that this protein is not expressed in all feline coronavirus infections; when expression does occur, perhaps because of a viral mutation allowing 7b expression, FIP may develop. Unfortunately, this test can't be used to confirm FIP because other infections can express the 7b protein.

Your vet needs to speak to the UC Davis lab. I'm probably right but this field changes rapidly. I might well be out of date with what UC Davis is doing.

Customer: replied 5 months ago.

too confusing. If we are trying to get this cat to a 0 titre to introduce it in the cattery which test do we use? This is assuming the cat is not shedding the virus which she is not.

Expert:  Dr. Michael Salkin replied 5 months ago.

I don't know which is preferable because I don't know what UC Davis is testing for. If you go with Antech, you would want to see a negative IgG and an IgM of 1:5 or negative...

Customer: replied 5 months ago.

I'll make it more confusing. A second cat in isolation has a UC Davis positive result at 1:1600 and an Antech result IgG <1.5 and I gM <1.10. Thats negative for Antech.

Expert:  Dr. Michael Salkin replied 5 months ago.

Once again, I'd be happy with Antech's results and wonder what UC Davis is testing.

Customer: replied 5 months ago.

Thats what I need an answer to.

Expert:  Dr. Michael Salkin replied 5 months ago.

Your vet has to give UC Davis a call. This is all I could find on the UC Davis site: "Coronavirus titers: Feline coronavirus titers may be used as an adjunct to diagnosis, however these only indicate whether a cat has been exposed to the near-ubiquitous FCoV. There are no titer tests specific for FIP. If the titer is negative at <1:25, it is likely the cat is truly negative and does not have FIP. It is important to remember that not all laboratories test down to such a low dilution, and a negative titer at higher dilutions (e.g. 1:400) is not meaningful. Very high titers (>1:1,600) are suggestive of FIP, however most cats with FIP do not have titers this high. Rising titers are less informative than they would be for other diseases, because cats with benign FCoV and those with FIP both cycle up and down in titer level. This is particularly likely in a shelter cat, who can be presumed to have suffered a recent onslaught of viral exposure. Occasionally, cats with advanced disease are seronegative due to severe immunosuppression."

Customer: replied 5 months ago.

So according to this my one cat with their 1:1600 is very high yet Antech is reporting the titer to be negative. Go figure.

Expert:  Dr. Michael Salkin replied 5 months ago.

The same blood wasn't tested. Remember that titers go up and down. 1:1600 to negative doesn't make a lot of sense to me, however.

Customer: replied 5 months ago.

My vet will need to call both.

Expert:  Dr. Michael Salkin replied 5 months ago.

Thank goodness. You must absolutely give me the skinny on this.

Expert:  Dr. Michael Salkin replied 5 months ago.
Hi Kathryn,

I'm just following up on our conversation about your pet. How is everything going?

Dr. Michael Salkin