Which test result should I trust?

I’m trying to figure out if:

a) there were false positive/negatives in the test

b) the girls are not infected but were exposed to the virus at one point (maybe even sample contamination)

c) the girls are carriers of PBFD with no clinical signs (the state of their plumage is very good considering the conditions they used to be kept in and mite infestation)

d) if they’ll ever be able to safely live with my pbfd free flock, regardless of what these results suggest.

It’s really important for me to know that because I can’t decide whether I should get them re-tested in 3 months and make a decision then or rehome them now. Please help!