"We appreciate the LaserCyte® analyzer's almost instant turnaround with results. We can start it and the VetTest®, leave to do x-rays and catheters, etc., and then come back for the results. This rapid information helps us monitor our patients more carefully because we can make treatment decisions in a few minutes as opposed to the next day. Our clinics love the accurate and repeatable results so much that we have just purchased our second LaserCyte analyzer."

Toby Carmichael, DVM
Lake City Animal Hospital
Acworth, CA

Visit IDEXX representatives at WVC to learn about two new products:
•  IDEXX VetStat® Electrolyte and Blood Gas Analyzer •  IDEXX Urine P:C Ratio
Event:	The Western Veterinary Conference
When:	February 21–23, 2005
Where:	Las Vegas, Nevada
Booth:	863

The Value of Sequential CBCs
By A.H. Rebar, DVM, PhD, DACVP
School of Veterinary Medicine, Purdue University

The complete blood count (CBC) is viewed as an essential part of the diagnostic evaluation of any sick patient. The CBC provides immediate information regarding the overall health status of the patient at the time of presentation. In particular, leukocyte data is used to determine whether the patient's disease is inflammatory, whether the animal is showing laboratory evidence of stress (high circulating glucocorticoid levels), whether there is evidence of tissue necrosis, whether there is evidence of systemic hypersensitivity (allergy), and whether there is evidence of neutrophil toxicity, which supports the presence of a relatively severe inflammatory process (most commonly associated with bacterial disease).

The erythrogram indicates whether or not anemia is present and, if present, whether it is regenerative (blood loss or hemolytic) or nonregenerative. Platelet counts are particularly important in animals that present for bleeding disorders. The vast majority of bleeding disorders in dogs and cats are associated with thrombocytopenia. Additionally, assessing platelet numbers is important in patients with serious inflammatory diseases. Mild to moderate thrombocytopenias (50,000/µL to 150,000/µL) in these patients may be a harbinger of emerging disseminated intravascular coagulopathy (DIC).

While using the CBC as part of the initial diagnostic work-up is extremely valuable, perhaps the greatest utility of hemogram evaluation is actually in following the clinical response of the patient over time.

Following the Leukogram
Sequential leukogram data is of particular value when following the response to therapy in animals with inflammatory disease. Leukocyte turnover in the blood is dynamic. The average neutrophil has a circulating half-life of 8–10 hours in health. In inflammatory disease, the circulating half-life of neutrophils may drop to less than an hour. This means that leukograms can change dramatically in a matter of hours and the changes that occur can give us a rapid indicator of how the patient is doing.

Following the Erythrogram
Sequential red cell analysis is of particular importance in animals with regenerative anemias. As in the case of white cells, there is an orderly normal production, release and turnover of circulating red cells. In the dog, the average circulating red cell lifespan is 100 days, while in the cat, the average circulating red cell lifespan is closer to 80 days. Because circulating red cell mass is kept constant, this means that in dogs, approximately 1% of the red cell mass is replaced daily with new young red cells (reticulocytes); whereas in cats, slightly greater than 1% of the cells are replaced each day. An increased number of reticulocytes (suggested by polychromasia on routine smears; confirmed with reticulocyte counts) in the blood indicates increased marrow production of red cells (regeneration).

An important concept to keep in mind is that loss of red cells due to hemorrhage or hemolysis (red cell destruction) is not immediately accompanied by release of increased numbers of reticulocytes into the blood. Increased production of reticulocytes, under the stimulation of the cytokine erythropoietin, must first take place in the marrow. As a general rule, it will take approximately 2–3 days after the initiation of a hemorrhagic or hemolytic event before reticulocytosis can be recognized in the peripheral blood. Maximal reticulocytosis can be expected to last approximately 3–4 days. If the regenerative process has been totally successful, the hematocrit will have returned to normal by approximately 10–14 days after a single hemorrhagic episode.

Clearly, gauging the appropriateness of the marrow's response to an anemia requires both an accurate history and sequential CBCs. For example, during the first 2–3 days of any anemia, regenerative or nonregenerative, the erythrogram would be classified as nonregenerative simply because there had been insufficient time for reticulocytosis to develop.

Sequential evaluation of red cells also is useful in judging response to therapy. Is steroid therapy resulting in reduced numbers of circulating spherocytes in cases of immune-mediated hemolytic anemia (IMHA)? Is iron supplementation causing regeneration in cases of iron deficiency or depletion? Is appropriate antibiotic therapy clearing the mycoplasma bodies from the blood in cases of feline infectious anemia (mycoplasmosis, previously identified as hemobartonellosis)? Is the hematocrit returning to normal appropriately following an episode of hemorrhage?

Following the Thrombogram
Sequential evaluation of platelets provides useful information in a variety of circumstances. For example, increased platelet counts are usually seen as an antecedent to reticulocytosis in regenerative anemias. Numerous large platelets are also usually a feature of this response. Thrombocytosis occurs because erythropoietin stimulates platelet production as well as red cell production. Because platelets have a shorter generation time than red cells, thrombocytosis is seen first in the peripheral blood.

Monitoring platelet counts is also extremely important in patients with serious inflammatory diseases. One of the life-threatening consequences of severe inflammation is disseminated intravascular coagulopathy (DIC). One of the first signposts of DIC is mild to moderate thrombocytopenia (50,000/µL to 150,000/µL). Whenever thrombocytopenia develops in association with an inflammatory leukogram, particularly when toxic neutrophils are also present, the possibility of DIC must be entertained.

Sequential platelet evaluation is also extremely important in animals receiving chemotherapy. Thrombocytopenia is one of the best indicators of drug-induced bone marrow toxicity. Platelet precursors are quite sensitive to various chemotherapeutic agents. Additionally, the short generation time and relatively short circulating time compared to erythrocytes for platelets leads to early recognition of potential marrow toxicity in the peripheral blood.

Hopefully, the preceding paragraphs help identify and illustrate the utility of sequential hematologic evaluation in veterinary practice. Numerous other examples could be recounted. Once the diagnosis is made, the work of the hematology laboratory is truly only beginning.

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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New Features in the Latest LaserCyte® and VetTest® Software Upgrades

LaserCyte software (version 1.30) and VetTest software (version 8.01) bring new benefits to you and the treatment of your patients.

LaserCyte software 1.30—provides the following new features and functionality:

• View the Features Guide

  The ability to graph the results of up to six tests for a single patient to show parameter trends and compare results over time
• Hyperlinks on the test results display interpretive guides, which offer valuable background information about the individual test parameters. This information can be printed and provided to your clients to help explain the significance of certain diagnostic results.
• The ability to schedule LaserCyte's clean cycle to accommodate your practice's schedule
• Support for the VetTest® analyzer's new Urine P:C Ratio

To ensure that you are operating with software version 1.30, tap the Instruments button on the main screen of your LaserCyte® touch screen, and then tap the System tab to view the software version.

VetTest Software 8.01—gives you the ability to run the VetTest analyzer's new Urine P:C Ratio, so you can detect urine protein loss and diagnose early renal disease with the first fully quantitative in-house measure of proteinuria.

In addition, each VetTest software upgrade provides calibration information for new lots of VetTest individual chemistries and prepackaged chemistry panels.

To ensure that you are operating with software version 8.01, either check the version number that prints on your patient results or, if no recent results are available, remove the software disk from the back of the VetTest and read the version number on the label.

If you are not currently operating on these latest software upgrades, please contact IDEXX Customer Support at 1-800-248-2483.

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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.

LaserCyte® Analyzer User Group Session

Monday, February 21, 2005, 6:30 p.m. to 9:30 p.m.
(gourmet buffet served at 6:00 p.m.)

Four Seasons Hotel
Desert Willow Room
3960 Las Vegas Boulevard South
Las Vegas, Nevada, USA 89119

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Parameter Trending for the IDEXX VetLab® System

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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

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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