Question about IFA Test Results

[Chris Behnke]

Here's the whole story.  When Monty was 8 months old, he became very sick.  When I took him to the vets, he was diagnosed as FeLV+.  At the time, the vet didn't think he would make it.  Now, a year later Monty is very healty.  He has never been sick since his diagnosis and has not shown any signs.  Because of this, we had him tested again.  The ELISA test came back with a very faint positive but the IFA test was negative.  What exactly does this mean?   Thanks, Chris Behnke