So. How reliable are vet's FIV tests? Are there different techniques, one more reliable than another?

Brought Paris and Zoe on for their 1-year checkups today - booster shots and a once-over. Also had Zoe tested for FIV. Both tested positive as kittens, Paris was negative at 6 mos, but Zoe still showed it. Well, she still came back positive. And she had a strong negative reaction to the shots - throwing up 9 times until we brought her back to the vet for further treatment.

BIL, who has two additional litter mates - both negative - doubts the veracity of the test. It seemed pretty easy - like a Pregnancy test - red is positive not-red is negative. Zoe's was pretty red. So, at ~15 mos old, is she now stuck with it? Any chance she'll come back negative at next years visit? Any chance the test is wrong and we should go to another vet to have her tested there?

Thanks, all.