Update: Well, MaryChristine is dead right when she says the "...experts can't agree". My vet called me back in response to my request for a serum ELISA and said he has *never* had a problem with using whole blood (though he'll be happy to do serum if that's what's wanted). So basically he's at odds with the (feline-specialty) vet on his staff who had told me serum was the ONLY way to go! (I did tell him about the fact she and I had spoken and that she had been emphatic about using serum.) He went online to a "vet only" website while we were on the phone and pulled up a word doc (2003), and an email (2008). The relevant info in the word doc appears to favor serum, plasma, saliva & tears; the email is from Susan Little DVM. But she's not talking from her own experience, nor does she make a categoric statement that whole blood is as accurate. She does say there were concerns in the past about using whole blood but "doesn't think" that's the current case. At any rate, I think we'll be doing an IFA next when funds allow. Unlike the vet on his staff, my vet didn't feel the necessity to start over with ELISA/serum. Kerry PS Not allowed to send the whole attachment to list, but if anyone wants it (possible outdated-ness notwithstanding) just let me have your private address and I'll forward.
Diagnostic Methods for Feline Viral Pathogens ACVIM 2003 Melissa A. Kennedy, DVM, PhD, DACVM Knoxville, TN introduction Diagnosis of viral infections of cats can be a challenge for the practitioner. Identification of the infectious agent involved in a disease is important not only for determination of the best treatment protocol, but also in terms of control and prevention. The variety of diagnostic assays available, the advent of newer molecular assays, and the differing recommendations that may be offered from diagnostic laboratories can be confusing. Interpretation of the results of the assays used also may not be straightforward-results may vary with the sample, methodology, and laboratory utilized. In an attempt to clarify some of the issues important in viral diagnostics, the general methodology of the available assays will be briefly described. Individual agents and the various diagnostic assays useful for each will be explained and include Feline Herpesvirus-1, Feline Calicivirus, Feline Parvovirus/Canine Parvovirus-2b, Feline Coronavirus, Feline Immunodeficiency Virus, and Feline Leukemia Virus. ............................ Feline Leukemia Virus Detection of viral antigen is the test of choice for feline leukemia virus. While viral antibody may be present, it does not provide information on whether the animal is persistently infected with the virus. Also, the use of the FeLV vaccine can complicate interpretation of results. The test used most commonly is the ELISA, of which there are a number available. This test assays for the p27 core antigen of FeLV and may be done on serum/plasma, saliva, or tears, depending upon the kit. IFA may also be used on whole blood smears. The ELISA is a sensitive assay, and can detect infection during the primary viremia. The majority of cats positive at this stage will go on to clear the virus, thus retesting of positive cats is required to determine the persistence of infection (2). IFA does not detect infection until the secondary viremia, after infection of precursor cells in the bone marrow; thus, animals positive by IFA are less likely to clear the virus (2). ELISA +, IFA-cats should be retested in 2-3 months; ELISA -, IFA + cats are uncommon and should also be retested. False positive results occur at a significant rate among ELISA kits (4). This can be due to the use in some kits of mouse antibody to capture the FeLV antigen, and the presence of antibody to mouse immunoglobulin in some cats (2). False positive results with ELISA's have also been documented due to the use of whole blood. False positive results using IFA have been documented with some anticoagulants (2). Therefore, use of fresh whole blood to make the smears is recommended. PCR has been investigated for detection of latent infections in bone marrow, but has not proven superior to ELISA/IFA combinations (5). REFERENCES 1. Andrew, Stacy E. (2000), "Feline Infectious Peritonitis", in Veterinar Clinics of North America, Small Animal Practice, September, 30(5):987-1000. 2. Barr, Margaret C. (1996), "FIV, FeLV, and FIPV: Interpretation and Misinterpretation of Serological Test Results", Sem. In Vet. Med. And Surg., August, 11(3): 144-153. 3. Burgesser, Kent M., Stephanie Hotaling, Anita Schiebel, Scott E. Ashbaugh, Steven M. Roberts, and James K. Collins (1999), "Comparison of PCR, Virus Isolation, and, Indirect Fluorescent Antibody Staining in the Detection of Naturally Occurring Feline Herpesvirus Infections" , J. Vet. Diag. Invest., March, 11:122-126. 4. Hartmann, K., R. M. Werner, H. Egberink, and O. Jarrett (2001), "Comparison of Six In-House Tests for the Rapid Diagnosis of Feline Immunodeficiency and Feline Leukaemia Virus Infections", Vet. Rec., September, 149:317-320. 5. Herring, E. S., G. C. Troy, T. E. Toth, S. D. Forrester, L. A. Weigt, and I. P. Herring (2001), "Detection of Feline Leukaemia Virus in Blood and Bone Marrow of Cats with Varying Suspicion of Latent Infection", J. Fel. Med. and Surg., 3:133-141. Kathryn Hahn on 09/24/2008 9:25:49 am ET *Posted In Message Boards 2.0 Hi there Just a quick question...when running an Idexx snap test for FeLV/FIV is there a preference for using whole blood vs serum vs plasma for the most accurate test result? Thank you! Susan Little on 09/24/2008 2:02:40 pm ET *Posted In Message Boards 2.0 Here's what the test kit insert says about samples: Serum, plasma or anticoagulated whole blood (e.g., EDTA, heparin), either fresh or stored at 2°-7°C (35°-45°F) for up to one week, can be used. For longer storage, serum or plasma can be frozen (-20°C/-4°F or colder) and then recentrifuged before use. Hemolyzed or lipemic samples will not affect results. In the past, there were concerns that using whole blood caused more inaccurate or hard to read results with the in-clinic ELISA tests, but I don't think there is current evidence that this is the case for the IDEXX Snap test. Susan Little DVM Diplomate ABVP (Feline) Ottawa, Canada [EMAIL PROTECTED] Roscoe Village Animal Hospital, P.C. 3131 North Clybourn Ave Chicago, IL 60618 773.549.3131 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of MaryChristine Sent: Saturday, November 22, 2008 8:09 PM To: email@example.com Subject: Re: [Felvtalk] ELISA & IFA okay, well, no one really wants to hear THIS one, but yes, using serum makes the odds that an ELISA is accurate MUCH MUCH higher. in fact, as recently as last november, a famous felv researcher (intials np) stated in a private note to someone other than myself that an ELISA done on whole blood is essentially useless. gee, great, this is at the same time that other "professionals' are trying to assure us that standard, done-at-the-vet's-office ELISA's (almost ALWAYS done with whole blood) are highly accurate. i just found out about this about a month ago, and still haven't digested it and what it means when the real experts (as opposed to those who just have chosen ignorance) can't agree. _____________________________________________________________________________ IRS CIRCULAR 230 NOTICE. 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