June 2006 Issue

Featured case study: Ten-year-old spayed female Labrador retriever with lethargy and lameness by Matthew Eberts, DVM, Lakeland Veterinary Hospital, Baxter, Minnesota

Physical exam

Plan
Because of the acute onset and severity of clinical signs, the potential of systemic disease was included in the differential. A general health screen, clinical chemistry profile, complete blood count and complete urinalysis were requested to investigate systemic organ disease and possibly characterize the severity of the disease process. Since there is history of tick-borne disease in this animal (previous Lyme-positive), a SNAP® 4Dx™ Test was requested to investigate for additional tick-borne infections.

Erythron—There was a minimal, normocytic, normochromic anemia, with no significant morphologic changes noted on the peripheral blood film to help identify the specific cause of the anemia. The most common cause for this type of anemia in dogs is inflammatory disease.

Leukon—There is a normal leukocyte count with the primary abnormality of a mild lymphopenia. Mild glucocorticoid influence is suggested, but because of the lack of a significant neutrophilia (the second most common leukocyte abnormality seen during a glucocorticoid influence), an abnormal leukocyte dynamic, possibly associated with inflammatory disease, must be considered. No left shift (presence of band neutrophil forms in circulation) and no neutrophil toxicity are noted on the peripheral blood film to support inflammation, however, the mild nonregenerative anemia is consistent with inflammatory disease. Identification of an active site of inflammation is required to confirm the presence of inflammation. No leukocyte-associated infectious agents were identified on the blood film.

Thrombon—The moderate thrombocytopenia identified on the hematology report is confirmed with evaluation of the peripheral blood film. Only an average of four platelets were seen per 100x oil objective field-of-view. Eight to ten platelets per 100x oil objective field-of-view should be minimally seen in an animal with normal platelet numbers. Few enlarged platelets were observed, which is supportive of the finding of an MPV (mean platelet volume—average size of platelet) greater than 20 fL and a PDW (platelet distribution width—objective measure of variability of platelet size) greater than 20%. MPV and PDW are typically less than 15–20 fL and 15–20%, respectively, in normal dogs. No platelet-associated infectious agents are seen on the peripheral blood film.

Kidney—There is mild azotemia (increased BUN and CREA), indicating decreased glomerular filtration. This finding, in the face of a nonconcentrated urine-specific gravity, is supportive of renal insufficiency. The marked proteinuria identified on the urine dry reagent strip is difficult to interpret in light of the hematuria present. No obvious cause for the hematuria is observed, however, potential underlying cystitis must be considered. Repeat urinalysis following clearing of the hematuria is recommended to further characterize the proteinuria.

Protein profile—The mild hyperglobulinemia is most likely associated with chronic antigenic stimulation. However, if underlying chronic infectious/inflammatory disease is not identified, further investigation with possible serum protein electrophoresis to better characterize the protein profile would be indicated.

Cholesterol—There is a minimal insignificant increase in cholesterol.

Additional Diagnostic Testing

Final Diagnosis
Co-infection of Lyme and anaplasmosis—Based on laboratory data and the clinical picture, a co-infection of Lyme and Anaplasma phagocytophilum is the most likely diagnosis. A send-out PCR test for Anaplasma phagocytophilum was performed at presentation. The test was positive, confirming co-infection, but these results were not available until 14 days after presentation.

Renal insufficiency

Discussion
Lyme infection—The clinic diagnosis of polyarthritis based upon physical examination is most likely associated with the Lyme infection. The potential of Lyme-associated glomerularnephritis and proteinuria would have to be considered. Significant proteinuria would have to be confirmed following clearing of the hematuria and repeat urinalysis, and a subsequent urine protein:creatinine ratio.

Anaplasma infection—The SNAP 4DX Test identifies both IgM (acute exposure) and IgG (chronic exposure) antibody responses to Anaplasma species, including Anaplasma phagocytophylum (previously known as Ehrlichia equi) and Anaplasma platys (infecting platelets). Thrombocytopenia is relatively common with Anaplasma phagocytophylum infection, and because it is uncommon with Lyme infection, the thrombocytopenia is most likely associated with the anaplasmosis.

Management

• Doxycycline—200 mg BID for 28 days
• Intravenous fluids

Outcome

• 24 hours after presentation—Fever resolved and Amber began eating and drinking well. Azotemia improved, but did not completely resolve with fluid therapy.
• 48 hours after presentation—Amber was ambulating much better and hematuria resolved.
• 72 hours after presentation—Diarrhea resolved.
• 7 days after presentation—Amber was clinically normal. CBC was within normal limits. Owner agreed to feed k/d® diet.
• 14 days after presentation—Amber went hunting and has done very well since (multiple hunting trips that season).
• 28 days after presentation—Follow-up profile and urinalysis showed persistent mild azotemia with nonconcentrated urine specific gravity. Hematuria and proteinuria were absent.

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 history, 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.

We want to hear from you. Let us know what you think about this case and tell us about any other case topics that you would like to see. E-mail us at diagnosticedge@idexx.com.

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Introducing direct digital radiography like you’ve never seen before
with the IDEXX-DR™ 1417 Digital Radiography System

The IDEXX-DR 1417 Digital Radiography System uses an innovative direct-capture technology that results in extraordinarily clear images that are an integral part of your diagnostic picture.

The system directly captures x-ray images, eliminating the light diffusion found in indirect capture technologies. Direct capture delivers unprecedented image sharpness and clarity. Images can be viewed within seconds and can be easily adjusted, annotated, stored, printed and transferred via IDEXX-PACS™ software.

IDEXX is committed to providing you with the latest technology to help you practice the best medicine possible, offering both computed radiography (CR) and direct digital radiography (DR) solutions for your practice.

For more information, contact IDEXX Digital Imaging Customer Support at
1-877-433-9922 or e-mail diagnosticedge@idexx.com.

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Add your practice’s name and information to your IDEXX VetLab® patient report

The IDEXX VetTest® Chemistry Analyzer and IDEXX VetLab® Station laboratory information management system (LIMS) allow you to add your practice’s name and address to the printed patient report. This gives you the option of personalizing your reports when providing them to your clients.

Depending on whether your VetTest® analyzer or IDEXX VetLab® Station (LaserCyte) computer is the hub of your in-house IDEXX VetLab® suite of instruments, follow these steps to change or add your practice’s name to the patient report:

My hub is the IDEXX VetLab® Station (LaserCyte) computer:

• Tap Settings on the Home screen.
• Tap the Reports tab.
• Tap the Report Header button.
• Type your practice’s name and address as you would like it to appear on the printed patient report.

My hub is is the IDEXX VetTest® Chemistry Analyzer (I do not have the IDEXX VetLab® Station (LaserCyte) computer)

• Press 5 on the main screen for the Settings menu.
• Press 4 on the Settings menu to access Printer Settings.
• Press 2 for Clinic Name/Address.
• Type your practice’s name and address as you would like it to appear on the printed patient report.

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Kitten season is here!
This is the third in our three-part series on quick tips for kitten season.

Kitten quick tip 3—Five steps to review with clients to keep kittens healthy (Plus, a $5.00 rebate offer for your clients!^† )

• Schedule a physical examination. Start with a thorough exam and follow up with a regular program of annual testing, vaccines and physical exams.

• Test for feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV). FIV and FeLV account for the most retrovirus disease-related deaths among pet cats. The American Association of Feline Practitioners (AAFP) recommends that all kittens be tested before entering a new household.* While there is no cure for FIV or FeLV, you can help your clients manage their pets’ diseases and help their cats lead happy lives.

• Check for and provide preventive treatment for parasites and infectious diseases. Regular screening and preventive treatment for parasites, such as ear mites, fleas, ticks, mosquitoes and fecal parasites, can help prevent the diseases and sometimes serious health problems associated with them.

• Vaccinate and take preventive measures to guard against disease. Vaccinations against the most common feline diseases can help your clients’ pets stay healthy. They include: rabies vaccine, feline panleukopenia (distemper) virus vaccine, feline herpesvirus, feline leukemia virus vaccine (for at-risk cats) and Calicivirus vaccine. The AAFP recommends testing before vaccinating for FIV and FeLV.

• Spay/Neuter all kittens! Spaying and neutering reduces the tendency for cats to mate or fight, and decreases their chance of contracting or spreading FIV or FeLV. It is recommended that all kittens undergo preanesthetic testing to determine overall health status and ability to tolerate anesthesia.

Rebate: Your clients can save $5.00 on an FIV/FeLV test for their kittens^†!

See kitten tip 1 in our April 2006 issue and tip 2 in our May 2006 issue.

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Education and Events

We offer a variety of training events about emerging trends and best practices in veterinary diagnostics in a forum designed to involve, educate and motivate you and your staff. Here are some of the upcoming educational events.
See a full listing.

Seminars

• Tick-Borne Diseases in Dogs
  Rick Alleman, DVM, PhD, DABVP, DACVP

Teleconferences

• Feline Immunodeficiency Virus and Feline Leukemia Virus: A Practitioner's View
  Lynn Buzhardt, DVM

Webinars

• The Most Commonly Misdiagnosed Diseases in Veterinary Medicine
  Fred Metzger, DVM, DABVP, and Peter Kintzer, DACIVM

Visit the education and events calendar, click the date to view the details, fill out and submit the form to register.

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Research Summary: Four methods, similar results—measuring total T₄ concentration in cats and dogs
by Dave Fisher, DVM, DACVP, IDEXX Reference Laboratories

Thyroid disease is common in both cats and dogs. One of the mainstays in the diagnosis of thyroid disease is the measurement of total thyroxine (T₄) concentration. There are multiple methods for measuring T₄ concentration, with radioimmunoassay (RIA) being considered the historical gold standard. A recent paper by Robert Kemppainen and Jeremy Birchfield in the American Journal of Veterinary Research (AJVR. 2006;67(2):259–65.) compares methods of measurement of this analyte.

This paper looks at four different methods of measuring T₄ concentration in dogs and cats. The compared methods include a human RIA kit, a canine RIA kit, a human chemiluminescent enzyme immunoassay kit and a point-of-care (in-house) enzyme-linked immunosorbent assay (ELISA) kit for dogs and cats (IDEXX SNAP® T₄® Test). The first three test kits are all routinely used in veterinary reference laboratories and have been validated for use in dogs and cats. The fourth kit is for use in-clinic and also has been validated for use in dogs and cats. In this paper, the different kits and methods are compared against each other, and includes animals with normal and abnormal T₄ values. Linear regression analyis and correlation coefficients are reported for all possible pairs of assays. In addition, bias plots are shown for the SNAP T₄ Test compared to each of the other methods.

The study demonstrates good correlation between the different methods. In general, the best correlation is noted at low- to mid-range values, with higher results demonstrating somewhat more bias. The SNAP T₄ Test shows good to excellent correlation with all of the tested kits, although, as noted, the bias charts and slopes of the regression lines indicate that higher results (roughly 6–8 µg/dL) do demonstrate more bias. The importance of this finding, as the authors note, is that reference values for the different testing methods may vary, but given accurate reference values, the different methods perform similarly in helping to determine whether an animal is hypothyroid or hyperthyroid.

The authors give suggested reference values for the compared methods, however, it is a well-recognized concept that test results should always be compared to reference values generated by the specific instrument and reagents, whether generated in-house or at a reference laboratory.

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NOW with FREE CE Credit!

Can you identify the cluster of crystals and single crystal indicated from this high-dry field-of-view of urine sediment with a neutral pH from a dog (unstained preparation)?

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