"We love the IDEXX Digital Radiography System's ease of operation and versatility that accommodates different users at our clinic. We can quickly enhance the image to suit the preferences of the individual user and improve our diagnostic capabilities.

As a referral hospital, our reputation depends on having the best quality x-rays. Films are expensive to take; they are time-consuming and tech-consuming. With the IDEXX Digital Radiography System, the quality of the image is so good, so easy to produce and so versatile, taking films the conventional way just seems old-fashioned.

The technology allows my practice to see, compare, enhance and magnify images. This and being able to save, print and e-mail the images brings us up to par with digital human medicine."

Gail Mason, DVM, MA, DACVIM
Portland Veterinary Specialists
Portland, Maine

Visit IDEXX representatives at ACVIM to learn about two new products:

IDEXX VetStat® Electrolyte and Blood Gas Analyzer	IDEXX Urine P:C Ratio

Feline Retrovirus Testing

Feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) are two of the most important diseases in cats. FIV is often described as a disease of "fighting cats," and is transmitted through bite wounds. FeLV, often described as a disease of "friendly cats," is transmitted in adult cats primarily through saliva. The prevalence of FeLV nationwide is 3.3%, and the prevalence of FIV is 3.4%.¹

Which cats should be tested?

According to the American Association of Feline Practitioners (AAFP), all newly acquired cats and kittens, sick cats and at-risk cats (those that go outdoors), should be tested for feline retroviruses.² Dr. Susan Little, of the Winn Feline Foundation and partner at the Bytown Cat Hospital in Ottawa, Ontario, adds these cats to the list:

• Cats with bite wounds or evidence of fighting
• Cats exposed to a known infected cat
• Cats that are going to be vaccinated against FeLV or FIV
• Cats that are going to be boarded in group housing³

FIV Testing

Antibodies can be detected in the blood about 60 days post-exposure to FIV, although it may be much later. Antibody ELISA is the most common method for FIV testing, with two tests available: the in-house IDEXX SNAP® FIV/FeLV Combo Test and the laboratory IDEXX PetChek® assay. The Western blot is the confirmatory test for FIV; however, in a recent study, the sensitivity and specificity of the IDEXX SNAP® FIV/FeLV Combo Test and IDEXX PetChek® for FIV were 100% and Western blot was 98% when compared to virus isolation.⁴ A small number of cats infected with FIV do not produce detectable antibody and will have a false-negative test on both ELISA and Western blot. Unfortunately, screening for FIV antigen is not possible because of the low level of circulating virus after acute infection.

Kittens can absorb maternal antibodies to FIV from their infected or vaccinated mothers that can take up to six months to be eliminated. Kittens born to FIV-positive queens may not develop antibodies to FIV, and the retrovirus status can vary within a litter, with some kittens being positive and some negative. Because of this variability in retrovirus status, pooling sera from a whole litter of kittens, just testing one kitten in a litter, or testing the queen for feline retroviruses is not recommended. These improper testing practices can lead to incorrect conclusions about the retrovirus status of the cats. This misinformation can then lead to problems for these cats and their new owners in the future. Animals that were thought to be negative for a feline retrovirus that are actually positive can develop clinical illness and potentially spread these diseases to other cats. The confirmatory test for FeLV is an IFA, although this test will not be positive until the virus has infected the bone marrow, which may be around 6–8 weeks post-exposure.

Most kittens that absorb maternal antibody in colostrum do not become infected and will test negative for FIV at six months of age. Because eliminating maternal antibodies takes a few months, some veterinarians often delay testing kittens for FIV. However, according to Dr. Julie Levy, associate professor of small-animal internal medicine at the University of Florida, "The value of testing kittens is that they're almost always negative. The strength of that negative test is very powerful. Delaying testing until six months means a lot of cats will never actually be tested. I have taken consult calls from other veterinarians on a handful of kittens that ultimately did prove to be persistently infected. Delaying testing until six months would allow these infected kittens to remain in a household, possibly exposing other cats."⁵

In July 2002, a dual-subtype, inactivated, adjuvanted FIV vaccine was introduced that contains subtype Clade A and subtype Clade D. This vaccine presents a problem for veterinarians trying to determine FIV status in cats because the antibodies produced by the vaccine cross-react with all currently available USDA-licensed tests, including the SNAP® FIV/FeLV Combo Test. Although PCR tests for FIV are available, several studies have shown that the sensitivity and specificity of different laboratories vary widely. In a study by Levy et al, the sensitivity varied between 41 and 93%. The specificity of nonvaccinated cats was 81–100% and that of vaccinated cats was 44–95%.⁶ In a study by Reggeti, sensitivity ranged from 59–90% between labs, but interestingly, 34–56% of vaccinated cats were false-positive.

FeLV Testing

The in-house IDEXX SNAP® FIV/FeLV Combo Test and laboratory IDEXX PetChek® assay test for the p27 core antigen of FeLV.

Feline immunodeficiency virus and feline leukemia virus are retroviruses that can significantly impact feline patients. Feline retrovirus testing should be part of a comprehensive wellness program for all kittens and cats when they visit their veterinarians.

IDEXX has many helpful diagnostic and communication tools available, including our Helpful Guidelines Diagnosing and Managing Patients with FeLV and FIV. Call 1-800-248-2483 to order your free copy (part #09-64990-00).

The recommendations contained in Diagnostic Edge educational materials are intended to provide general guidance only. As with any diagnosis or treatment, you should use clinical discretion with each patient based on a complete evaluation of the patient, including physical presentation and complete laboratory data. With respect to any drug therapy or monitoring program, you should refer to product inserts for a complete description of dosages, indications, interactions and cautions.

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Introducing the IDEXX VetStat® Electrolyte and Blood Gas Analyzer
Easy, accurate electrolyte and blood gas analyses when fast medical information is needed

• No time-consuming temperature equilibration
• Frees up your limited refrigerator space
  
  

• Simple menu navigation, VERY EASY TO USE
  
  

• Eliminates underfilling or overfilling of cartridge
• Ensures consistent sample insertion
  
  

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Education and Events
We offer a variety of seminars and teleconferences about emerging trends and best practices in veterinary diagnostics—in a forum designed to involve, educate and motivate you and your staff.

• Visit the seminar and teleconference calendar and click the date to view the details.
• Fill out and submit the form to register.

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NEW Educational Video Available: Preparing a Blood Film

The importance of the blood film as an essential complement to an automated CBC has been highlighted in various past issues of the Diagnostic Edge, such as in the technical tip of the March 2004 issue and the education article in the March 2005 issue. To further assist in helping those just learning how to prepare a blood film, as well as anyone just needing a bit of a refresher, IDEXX has created an easy to follow video (2.6 MB) to be used as a training tool right in the clinic.

For any questions pertaining to the importance of blood-film analysis or how to prepare one, please write to the Diagnostic Edge.

Did you know that you can purchase IDEXX VetCollect® tubes separately?

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Calling All Qualified Urine Protein:Creatinine/Renal Disease Case Studies

Do you have a case study in which a urine protein:creatinine ratio helped you detect renal disease? If so, you could win a copy of Renal Disease in Dogs and Cats by Dr. Jonathan Elliott and Dr. Scott Brown, just for sending us a qualified submission!

The case that best exemplifies how clinics can "practice what's possible" will be featured in a special edition case study booklet on renal disease and proteinuria.

Qualified submissions must include:

• The patient's name, signalment, history, physical examination, bloodwork and a complete urinalysis (including an IDEXX Urine P:C Ratio result)
• A diagnosis of renal disease (either primary or secondary)
• The name, address and telephone number of your clinic; and the names of your veterinarians and veterinary technicians
• Pictures, if possible

Cases must be submitted to the following address:
Dr. Michelle Kahn
Attention: UPC/Renal Disease Case Study
IDEXX Laboratories
One IDEXX Drive
Westbrook, Maine 04092

Limit one case per practice.

If you have any questions, please contact your IDEXX representative or call Dr. Michelle Kahn at 1-207-556-8589.

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