Well, the SNAP could indeed be wrong, Most vets now use the 3-way SNAP tests -
FIV+FeLV+Heart Worm. Our shelter had horrible problems with these tests
producing false negatives. We stopped using them. We got ahold of the old tests.
Is the anemia better now? I think you said it was up to 15% from 10%, thought
it's my understanding that that can vary, too by whether or not the cat is
being given fluids.
Beth
Don't Litter, Fix Your Critter! www.Furkids.org
________________________________
From: David Arthurs <arthurs.da...@gmail.com>
To: felvtalk <felvtalk@felineleukemia.org>
Sent: Thursday, December 27, 2012 1:02 PM
Subject: Re: [Felvtalk] Re anemia and negative IFA (Dave)
Thanks for your reply Beth. I'm an engineer and I'm trying to make sense out of
the tests...and what you said isn't all making sense to me yet :).
The kittens had been separated from their mother for most of their lives. The
mother was an outside-cat and died/disappeared right after the kittens were
born. My nephew hand-fed the litter and we adopted two of five original
kittens. They would have been un-exposed to other cats for more than six months
before we tested them originally. The original Elisa should have been positive
because we had them for 90 days before spaying them and they were in my
nephew's care for many more months before that. The vet also latches onto that
period as originating their exposure to the virus...because nothing else makes
sense. The cat community lives in my sister's barn in a rural section of
Wisconsin...she has put many cats up for adoption and has never had a case of
FeLV in any of the their cats to date.
The IFA detects viral protein either in the blood or blood cells. If Tux had
anemia from FeLV itself then the virus would have to be very active in the bone
marrow and blood, or, her immune system was compromised and she got a parasitic
infection...also involving FeLV in the bone marrow. In both cases, with
something as severe as anemia presenting, the IFA would be positive. It doesn't
make sense that the IFA could be negative under these circumstances. From what
I read you don't get anemia on initial exposure to the virus...the anemia is a
side effect of serious infection of the bone marrow and white blood cells.
Here is what I read about the snap test online (considering the source):
1) There is room for interpretation of the results by the technician (color
detection). Sometimes the color is very faint or an over-zealous tech can see a
faint color when there is none.
2) Some other antibodies in the blood can cross-react with the elisa...giving a
false positive.
3) First two issues aside, the test is 95% accurate. IFA is over 99% accurate.
Thanks again for your reply...I guess I'm having a hard time understanding why
the IFA was negative in such a severe case of anemia and how Tux could ever
have been exposed to the virus.
Thanks. Dave
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