January 2006 Issue

Featured Case Study:
Eight-year-old neutered male Labrador retriever, Prescott
by Peter Kintzer, DVM, DACVIM, Boston Road Animal Hospital, Springfield, Massachusetts, and Dennis B. DeNicola, DVM, PhD, DACVP, Chief Veterinary Educator, IDEXX Laboratories

Physical Exam

Prescott is bright, alert and responsive. Temperature, pulse and respiratory rates are normal. The only physical abnormalities beyond obesity are related to the ear canals and the skin. The aural canals are inflamed, narrowed and contain a large amount of brown waxy discharge. Scattered papules, pustules, crusts and excoriations are present on the ventral abdomen.

Erythron—There is a minimal normocytic, normochromic anemia. The anemia is nonregenerative at this time because the reticulocyte count is less than 60–80 K/µL. No morphologic abnormalities were noted during blood-film evaluation.

Leukon—There is a mild leukocytosis characterized by a minimal to mild mature neutrophilia, minimal lymphopenia to low normal lymphocyte count, minimal monocytosis and eosinopenia. No immature neutrophils, toxic neutrophils or other morphologic abnormalities were noted during blood-film evaluation. Possible interpretations include glucocorticoid influence (“stress”) alone, or inflammation with superimposed glucocorticoid influence. The mild monocytosis is consistent with either glucocorticoid influence or inflammation associated with a tissue demand for macrophages. The presence of a minimal nonregenerative, normocytic, normochromic anemia is potentially associated with inflammatory disease, but the presence of the glucocorticoid influence precludes accurate identification of inflammation.

Thrombon—Platelet numbers are within reference range limits and this is confirmed with a brief blood-film evaluation. No significant morphologic abnormalities were noted.

Chemistry—The chemistry panel and electrolytes are unremarkable except for elevated cholesterol. This could be associated with a nonfasted sample, diabetes mellitus, pancreatitis, hyperadrenocorticism, hypothyroidism, nephrotic syndrome and cholestatic liver disease.

Total T₄—The total T₄ concentration is below the reference range. The low total T₄ concentration can be the result of episodic secretion of T₄ in a normal dog, nonthyroidal illness (euthyroid sick syndrome) or hypothyroidism. Episodic secretion of thyroid hormones by the thyroid gland can result in the serum total T₄ concentration being below the reference range at random time points during any given day. The lowering of total T₄ concentrations by nonthyroidal illness is well-described. The diagnosis of canine hypothyroidism should never be based on a single low total T₄ level (especially in dogs with nonthyroidal illness). A low or low-normal total T₄ level should be followed by determination of free T₄ by equilibrium dialysis and cTSH levels (at the reference laboratory) to confirm or exclude a diagnosis of hypothyroidism. The finding of a total T₄ concentration in the upper half of the reference range (2–4 μg/dL) makes a diagnosis of hypothyroidism very unlikely. The determination of total T₄ levels is very useful as the initial screening test for canine hypothyroidism.

Additional Diagnostics: Cytology of the otic discharge

There are numerous normal superficial cornified squames and much keratinous material mixed with moderate numbers of mature and mostly nondegenerate, but often mechanically broken, neutrophils. Moderate numbers of extracellular budding yeast organisms consistent with Malassezia organisms (arrows) are observed. Few macrophages are present.

Interpretation: Moderate neutrophilic inflammation associated with yeast overgrowth; changes consistent with chronic otitis externa

Differential Diagnosis

Malassezia otitis
Bacterial pyoderma
Suspect hypothyroidism

Plan

The plan is to initiate appropriate antimicrobial therapy, including topical antifungal, anti-inflammatory ear medication and an oral antibiotic course of appropriate duration. A free T₄ by equilibrium dialysis and cTSH were requested at the reference laboratory.

Confirmatory Test Results

Increased canine TSH values may occur in dogs with untreated primary hypothyroidism. Sick euthyroid dogs are expected to have low-normal TSH concentrations. Secondary or tertiary hypothyroidism (pituitary or hypothalamic lesions) is reported to occur in less than 5% of hypothyroid dogs.

Final Diagnosis

Confirmation of hypothyroidism

Clinical Case Outcome

Thyroid hormone replacement therapy with L-thyroxine given every 12 hours was begun. Response to therapy is monitored by regular determination of total T₄ levels and resolution of clinical signs. Therapeutic monitoring of total T₄ levels was instituted, first at six weeks after initiating therapy to ensure an appropriate dosage of L-thyroxine was being administered. Total T₄ levels should then be checked at least every six months, and six to eight weeks after any change in dosage.

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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Announcing the Spec cPL® (canine pancreas-specific lipase) Test from IDEXX Reference Laboratories

Redefine the way you diagnose pancreatitis in dogs—use this revolutionary new test to help you quickly and confidently rule it in or out.

Canine pancreatitis is a potentially fatal disease and is difficult to diagnose. Presenting signs are common and nonspecific, including vomiting, anorexia and abdominal pain.

The new Spec cPL Test finally offers you more definitive diagnostic results. Although not as specific as the Spec cPL Test, serum amylase and lipase can be performed quickly with in-house analyzers. Pet-side amylase and lipase provide early warning for pancreatitis, while the Spec cPL assay will help you confirm the diagnosis.

View a comparison chart to see the difference between the Spec cPL Test and other diagnostic methods.

The Spec cPL Test is an enhancement of the cPLI test developed by Dr. Jörg Steiner and Dr. David Williams (Texas A&M University GI Lab). IDEXX scientists worked with these doctors to create a fast, accurate test you can trust. With greater than 95% specificity and sensitivity, this test far outperforms other test methodologies, so you can treat confidently. Tests are run daily at IDEXX Reference Laboratories, so you can move ahead quickly with treatment.

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Sampling lymph nodes for cytology
by Peter Fernandes, DVM, DACVP, clinical pathologist, IDEXX Reference Laboratories

1. Introduce the needle into the lesion with or without a syringe attached. If a syringe is used for better control of needle placement, we recommend drawing a few ccs of air into the barrel before placing the needle into the tissue. This allows rapid expulsion of the tissue after the collection process is completed.
2. The needle passes through the skin into the tissue. Move the needle rapidly in and out at a single angle to obtain many tiny, cylinder-shaped core biopsies. Keep the needle beneath the skin or within the lesion, and use eight to ten long strokes at the rate of approximately three per second.
3. While remaining within the lesion, the direction of the needle can be changed at least two to three times to collect tissue from different areas of the lymph node. If tissue or blood is noted in the hub of the needle, the procedure should be stopped immediately.
4. Expel the collected specimen onto a clean glass slide for further processing. If a syringe is used during the collection process, the expulsion is more rapid and may allow a better cell yield.

5. Gently lay a second slide (spreader slide) on top of the aspirated tissue, giving the tissue enough time to diffuse into a thin layer.
6. Move the spreader slide to the opposite end of the sample slide. Care should be taken not to apply downward pressure to the spreader slide. Also, if the spreader slide is run straight off the end of the sample slide, you could lose large sheets or clumps of tissue.
7. The smeared specimen should take on a target-like appearance, with blood and fluid encircling a central area that contains most of the tissue of interest.

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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.

Webinar

• Uncover Early Renal Disease: Integrate UPC Ratios into Your Practice
  Fred Metzger, DVM, DABVP and Michelle Kahn, MS, DVM

Seminars

• The Most Commonly Misdiagnosed Diseases in Veterinary Medicine (NAVC lunch)
  by Fred Metzger, DVM, DABVP
• How to Manage Retrovirus-Positive Cats (NAVC lunch)
  Susan Little, DVM, DABVP (Feline)
• Diagnosing Canine Pancreatitis (NAVC lunch)
  David A. Williams, MA, VetMB, PhD, DACVIM, DECVIM-CA and Jörg M. Steiner, med.vet, Dr. med.vet, PhD, DAACVIM, DECVIM-CA

Visit the education and events calendar to view the complete list of IDEXX-sponsored lunches at NAVC. Choose the date to view the details, fill out and submit the form to register.

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Use a recall report to close compliance gaps for therapeutic diets
by Wendy S. Meyers, Communication Solutions for Veterinarians, Denver, Colorado

When a dog’s symptoms indicated possible food allergies, a doctor recommended a hypoallergenic diet and explained how to make the food transition. He emphasized no treats or table scraps during the food trial. Two days later, a technician called to check on the diet transition. The client said, "My kids are responsible for feeding Duke. At first, he wouldn’t eat the new dog food so they squirted Vita Gravy over it and then Duke happily finished every kibble." While enticing the dog to eat had good intensions, it ruined the food allergy trial. The technician again explained why the hypoallergenic diet needed to be the sole food source—no Vita Gravy, treats or table scraps. A simple callback quickly identified and corrected this problem.

Running a daily recall report on your veterinary software can remind you when clients need follow-up calls to monitor patients’ progress. Best of all, these calls close compliance gaps or clarify misunderstood instructions. For example, the first time any therapeutic diet is prescribed, enter a two-day callback. A technician calls to make sure the client has made the food transition and is following strict feeding instructions.

In the 2003 AAHA study, A Path to High-Quality Care, compliance for therapeutic diets was 19% for dogs and 18% for cats, with 11.6 million dogs and 9 million cats diagnosed with conditions a therapeutic diet could have helped.

Without this callback, the opportunity to recapture compliance would have been missed. Had the client continued to use Vita Gravy, the food allergy trial would have failed, resulting in a chronically itchy, uncomfortable patient. An entire year might pass before the client receives reminders for a wellness exam and vaccinations. In the passing year, the food allergy problem worsens, the client loses confidence in the veterinarian, and the doctor assumes instructions were followed and the problem was resolved.

Close the gap on compliance for therapeutic diets by creating a protocol for follow-up the first time a diet is prescribed. Your clients will appreciate your personalized service, staff members will value their vital roles in compliance and the patient will get needed medical care.

Wendy S. Myers owns Communication Solutions for Veterinarians in Denver, Colorado, and provides consulting services on client service, marketing and hospital management. She is the author of two books and four videos. You can reach her at 1-720-344-2347 or visit www.mycommunicationsolutions.com.

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Can you identify these cells?

Peripheral blood film from a dog with persistent leukocytosis (Wright's stain).

1. Identify the cell indicated by "A"
2. Identify the cell indicated by "B"
3. Identify the structure indicated by "C"

Send your answer in an e-mail to diagnosticedge@idexx.com. Please include your name, practice name, address and telephone number.

The first 10 respondents to correctly identify the cells and structure will appear in the next issue of the Diagnostic Edge.

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