RE: VecTest Results

Dr Ward Stone,

Thank you for the data. Two things to point out:

(1) Use of VecTest antigen detection assay in detection of virus antigen in
tissue samples has been carried out on purely exploratory basis in this
study. This is not recommended and emphatically stated so earlier (my
correspondence dated 6/10/03 attached herewith).

(2) It would be worthwhile to figure out why an antigen detection test such
as VecTest would be positive or negative in the oral swabs where its best
use could be - in rapid dead bird analysis or surveillance area. Any
quantitative data on the concentration of the virus in the 4+1 corvid oral
samples that were falsely positive and the two samples you mentioned that
are false negatives?

The part of the data where the test is used properly such as on oral swabs
in your study (attached herewith) is good information and when supported
with quantitative data could be used for determining caution in use for oral
swab analysis of corvid/non corvid species.

And again I want to reassure you and others copied on this email that if the
data from proper use does not support usefulness of the product, we will
discontinue providing the product for that use. We want to provide the best
and reliable tools. Therefore feel free to provide feedback.

Regards,

Kirti

Kirti Davé PhD
Team Director
Medical Analysis Systems, Inc
5300 Adolfo Road
Camarillo, CA 93012
Phone: (805)-987-7891 ext 6-3214
Fax: (805)-383-8260
email: kdave@mas-inc.com

-----Original Message-----
From: Joseph Therrien [mailto:jetherri@gw.dec.state.ny.us]
Sent: Tuesday, July 01, 2003 1:47 PM
To: nap4@cdc.gov; nck6@cdc.gov; lcl3@cornell.edu; Roscoe@eclipse.net;
campbell@gw.dec.state.ny.us; ldk02@gw.dec.state.ny.us;
mxe04@gw.dec.state.ny.us; ebk01@health.state.ny.us; kdave@mas-inc.com;
doug docherty@usgs.gov; esaito@usgs.gov; kathy_converse@usgs.gov
Subject: VecTest Results

Cautions on use of the VecTest for West Nile Virus diagnosis in birds.

The attached table shows the frequency of false positives for WNV in
birds tested to date with the VecTest. Although oral false positives are
relatively low in percentage, they nevertheless are significant. From
the literature we had not expected this level of false positives in the
oral tests. False positives for WNV were common in the tests run on
kidney and liver samples. At this point New York has only two birds that
are WNV positive by PCR. Both of these are crows with false negatives by
VecTest.

As the season progresses we anticipate numerous WNV infected birds to
arrive at our lab and this will provide many cases, of a variety of
species, to check for false negatives.

Our data indicates that the use of the VecTest should be used with
caution and that the VecTest seems to need more adjustment and/or
development before it is fully acceptable as a diagnostic aid for WNV in
birds.

Dr. Ward B. Stone
Wildlife Pathologist
Wildlife Pathology Unit
108 Game Farm Road
Delmar, Ny 12054

Phone (518) 478-3032
Fax (518) 478-3035

attached mail follows:

Dr Stone,

The VecTest kits/assays are not intended to be used on any tissue (tissue
extracts). From the results you sent, amongst all samples tested there are
two oral swabs out of which only one of them is from a corvid that has
tested positive. For this sample I would ask you to repeat the PCR and
VecTest again. Also it would be worth while to check out with another
antigen based assay such as ELISA.

The last sample from Westchester which tested positive by PCR but negative
with VecTest, was that a marginal virus amount?

The test kits we market presently are for the use with mosquito samples
only. Do you test these? The use of VecTest WNV Antigen assay for oral swabs
collected from corvids appears to be working for labs that have initiated
these type of use. The problems that would come up would be when the kits
become a tool for any kind of exploratory work. The reagents used in the
dipstick assay are monoclonals and to avoid nonspecific interactions with
IgGs from other species and/or other components, one would need to modify
the current format of the dipstick.

The data presently at the AMCA March, 2003, from oral swabs from corvids is
good enough to continue using the VecTest for that purpose. This data is
still being collected so that we can market a kit for that purpose.
Regarding cautions from findings about exploratory uses such as tissues and
other species, we will be open and point that out to the customers. The kits
were never meant to work in every and any sample.

I would be grateful if you provide me more quantitative data on corvid oral
samples where VecTest provided a result different from the PCR. That data
would have meaning for other customers and for something to check out for
scientific interest and a just evaluation of a new rapid assay tool. I hope
you will be open and continue to provide me feedback.

Thanking you,

Best Regards,

Kirti

Kirti Davé PhD
Senior Project Manager
Medical Analysis Systems, Inc
5300 Adolfo Road
Camarillo, CA 93012
Phone: (805)-987-7891 ext 6-3214
Fax: (805)-383-8260

-----Original Message-----
From: Ward Stone [mailto:wbstone@gw.dec.state.ny.us]
Sent: Tuesday, June 10, 2003 12:56 PM
To: kdave@mas-inc.com
Subject: Problems with West Nile Virus VecTests

In testing the VecTest West Nile Virus Antigen Assay that your company
supplied to the Wildlife Pathology Unit of the New York State DEC, we have
found a number of problems with false positives. Although we will be
carrying out extensive further testing, the data we have to date causes me
not to use your companies VecTests for diagnosing the presence of West Nile
in birds - including crows.

Are other laboratories/scientists experiencing similar difficulties with the
VecTest?

Attached is a summary of our data as to noon today. I am especially
concerned that people may be using at least some test kits that your
company has supplied that are unreliable.

Ward B. Stone BA, MS, SC.D
Wildlife Pathologist II
New York State Department of Environmental Conservation
Wildlife Pathology Unit
108 Game Farm Road
Delmar, New York 12054
Phone (518) 478-3032
Fax (518) 478-3035