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Subject: [WNV-L] Efficacy of VecTest for WNV Detection
Date:
July 3, 2003
Posted by:
Lois Levitan (lcl3@cornell.edu)
Ward Stone (wbstone@gw.dec.state.ny.us)
Kirti Dave (kdave@mas-inc.com)
The following is a series of correspondence between Ward Stone, Wildlife Pathologist with the NYS Department of Environmental Conservation, and Kirti DavŽ, Team Director at Medical Analysis Systems, Inc., which developed the VecTest. The first memo [1] was written to me, in response to my request for permission to post the correspondence to the WestNileVirus-L listserv (since I had been included on the exchange as an individual not as listserv moderator). Other memos are in the order they were written, from earliest to most recent. -- Lois Levitan [1] Permission to post [2] Problems with West Nile Virus VecTests. June 10, 2003. Ward Stone to Kirti Dave [3] Response to "Problems." June 10, 2003. Kirti Dave to Ward Stone [4] Cautions on use of the VecTest for West Nile Virus diagnosis in birds. July 1, 2003. Ward Stone to Kirti Dave and recipient list [5] Response to "Cautions on use of VecTest." July 1, 2003. Kirti Dave to Ward Stone and recipient list. ----- [1] PERMISSION TO POST Date: Thu, 03 Jul 2003 12:51:49 -0400 From: Ward Stone by way of "Joseph Therrien" <jetherri@gw.dec.state.ny.us> To: <lcl3@cornell.edu> You can post our data on the VecTest on the West Nile Virus-L listserv. I am also transmitting our previous email from my unit to and from Dr. Dave. I had hoped that organ tissues (e.g. brain, kidney, liver, spleen) would show more accuracy and precision for the presence of WNV antigen than the oral epithelium. This does not seem to be the case, but the oral swabs also show a significant false positive and false negative problem - even in corvids. Dr. Ward B. Stone M.S., sc. D. Wildlife Pathologist NYS Department of Environmental Conservation Wildlife Pathology Unit 108 Game Farm Rd Delmar, NY 12054 ----- [2] PROBLEMS WITH THE WEST NILE VIRUS VECTESTS >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 ----- [3] RESPONSE TO "PROBLEMS WITH THE WEST NILE VIRUS VEC TEST" >From: Kirti Dave <kdave@mas-inc.com> >To: 'Ward Stone' <wbstone@gw.dec.state.ny.us> >Subject: RE: Problems with West Nile Virus VecTests >Date: Tue, 10 Jun 2003 14:32:25 -0700 > >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 DavŽ 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 ----- [4] CAUTIONS ON USE OF THE VECTEST FOR WEST NILE VIRUS DIAGNOSIS IN BIRDS >From: Ward Stone by way of 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 * See http://environmentalrisk.cornell.edu/WNV/WNVEducDocs/VecTestTissueResults.xls --- [5] RESPONSE TO "VECTEST RESULTS" Date: Tue, 1 Jul 2003 16:13:40 -0700 From: Kirti Dave <kdave@mas-inc.com> To: [recipient list for Ward Stone's message] Subject: 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 DavŽ 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 -- Lois Levitan, PhD Program Leader Environmental Risk Analysis Program Department of Communication and Center for the Environment 213 Rice Hall, Cornell University Ithaca, New York USA 14853-5601 Phone: (607) 255-4765 Fax: (607) 255-0238 Email: LCL3@cornell.edu Web: http://environmentalrisk.cornell.edu---------------------------------------------------------------------------- WESTNILEVIRUS-L is an email discussion group for communication and discussion about West Nile Virus, particularly regarding policy, risk reduction and public education issues. It is moderated by Dr. Lois Levitan, Program Leader of the Cornell Environmental Risk Analysis Program. Subscribers are encouraged to post to the group by sending an email to: WESTNILEVIRUS-L@cornell.edu. 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