To the FML:
 
I've been involved in a recent discussion concerning possible false
positive results by CIEP for ADV Antibody along with Drs.  Williams and
Bloom.  It is my contention that a false positive reading is possible for
two reasons (I respond here with some of the same language used prior in
this discussion):
 
First, the basis of potential false positive results would not be
cross-reactivity with distemper virus, antibodies to distemper or any other
virus (including parvovirus) or their antibodies.  The basis for this is
the production in ferrets of antibodies to cellular debris in vaccines,
present as a by-product of their manufacture in cell culture.  Similar
cellular debris may be present in the whole ADV viral lysate (actually a
mixture of several ADV-related proteins, or antigens) used in the test.
When antibodies to this debris in the ferret serum encounter the ADV lysate
in the test a precipitate line can be formed which is similar to an ADV
Antibody positive.  Especially in cases where the ferret is tested by this
technique within 2-3 months of receiving a vaccine I believe there is some
likelihood of a false positive result due to this phenomenon.  Even United
Vaccines notes the possibility of false positives from recently vaccinated
ferrets.
 
Second, and admittedly subjective, is the issue of reading results.  As I
understand it, the CIEP result is determined by an operator's judgement as
to whether a precipitate line is formed in the gel, which is a subjective
method itself.  In my conversations with Dr. Bloom, he indicated that with
any questionable result in his laboratory, the CIEP gel is washed and
further treated with a protein dye stain for better visual detection, and
the interpretation thus confirmed.
 
I don't wish to contradict Dr. Williams, but I must respectfully add that
Dr. Bloom did not say outright there are no false positives associated with
CIEP.  He points out that there conceivably are false positives, but there
is no peer-reviewed evidence to prove it or the contrary.  As I mentioned,
even United states concerns about testing around the time of vaccinations.
While I have not seen data as to the accuracy, sensitivity or specificity
of CIEP, I agree that anyone who has a CIEP positive ferret should take
appropriate steps to isolate the ferret and not equivocate, because of the
nature of the danger involved.
 
As a disclaimer, let me say that my organization is one of the groups
mentioned by Dr. Williams as being involved in the development of a new
diagnostic tool for ADV Antibody.  I do think that the ELISA we've
developed is a better diagnostic test for ADV Antibody for several reasons.
When we are finished with our clinical/other studies I will demonstrate
this with the data in the appropriate forum.  I plan on being at the
Pennsauken show on December 2, and would be happy to discuss these issues
with all present.
 
Sincerely,
Robert L. Stephon, Ph.D.
Avecon Diagnostics, Inc.
[Posted in FML issue 3223]