yes, it is possible for a cat who tests positive on the IFA to test negative
later on, but it is MUCH less likely.

depends on two things, as far as i can tell, on two things: initially, the
same thing that holds for retesting with the ELISSA: it can take up to 120
days for the antigens to the virus to work their way out of the cat's system
and after a positive test, to be negative on a second ELISSA test (or on an
IFA--they test for the same thing, just in a different form), so if you
perform an IFA too soon after an ELISSA, it's just gonna be reacting to the
same antigens.

that's why we emphasize the need to WAIT for the exposure period to pass--i
don't trust a second test until after 120 days, unless i know for sure when
the last possible exposure was.

in some cases, and this is the research citation i can't find, tho it used
to be in an older version of the merck, is that one cat didn't test negative
on an IFA until seven or eight months after his first test! we just don't
know enough....

generally, however, if a kitty tests positive on the IFA AFTER the 120-day
period, in the vast majority of cases, it will remain positive.

just today i started looking for more information that was mentioned in
november about the newest research showing that some cats can remain
positive without ever progressing to symptoms, AND not remaining contagious.

as i say all the time, we just do NOT know enough, because for too many
years, the main mode of treatment was euthanasia, which makes it very
difficult to do research. you have to have a living population to learn
anything, after all.

(and yes, it takes up to 120 days for the antigens to show up on the
ELISSA/IFA, as well, so a NEGATIVE test doesn't mean a thing either, but
look at how few cats who test negative ever end up positive. some do, sadly,
but the vast majority never do..... )


On Wed, Apr 8, 2009 at 5:28 PM, James Rauscher <> wrote:

> Thank you for the info, MC! Onyx's IFA test came up positive - do you know
> if cats who are positive on that test ever revert to negative? Also, some
> vets say that vaccinated cats always show up positive on later tests
> (because of the vax), but two of them said that vaccinated cats do not show
> up positive on the IFA test unless they actually have the virus. Can anyone
> clarify that for me?
> Avia
> _______________________________________________
> Felvtalk mailing list

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