Like everyone else I am still learning.
 
One thing that i have noticed, though: when folks get a positive test
result back they tend to not retest.  Why?  Well, I guess because once
there is a positive test you have to act as if it is a true positive
because false negatives are more common, so why re-test?  There are two
upshots of this:
 
1. It better protects ferrets by going the extra mile with precautions.
   but
2. It makes it impossible to get any handle on the rate of false
positives -- which appears to be low but exactly how low isn't known
because many folks see no reason to re-test as long as they have to be
just as careful, anyway.  (NO test is ever 100% accurate in either
direction.  As Birdwhistle stated, "Absence of evidence is not evidence
of absence."
 
I am not among the folks out there who know the most about this by a long
shot, but i do remember back to the old Dark Ages both before and when
James Fox first announced in his first edition of _Biology and Diseases of
the Ferret_ that Aleutian Disease had been found in ferrets and how some
members of the ferret community insisted that was just not so, and I
remember when Parvo tests were all anyone had and that they were terribly
inaccurate.
[Posted in FML issue 3686]