need help - a negative, later positive - ?

[Gloria B. Lane]

I've got a question - our group took in a kitten from animal control , 8 
weeks old, in May 2003.  He was tested for FELV/FIV (Elisa snap test)  in 
November 2003, and tested negative. We adopted him out about March 
2004.  The new owner just reported back that he was havine URI problems, 
and he tested positive for FELV.

I've heard that tests on kittens aren't dependable.  Any insight into this?
Gloria