Hematology in Practice

Indications for Hematology

The complete blood count (CBC) provides a broad overview of the general health status of the patient.

> Peripheral blood serves as a transport medium between the bone marrow and tissues.

>The CBC therefore provides a "snap-shot" of the hematopoietic system at a specific point in time.

Complete blood counts are recommended in the laboratory evaluation of every sick patient, every pre-anesthetic evaluation, every senior/geriatric profile, and as a recheck test for patients previously diagnosed with erythrocyte, leukocyte, or platelet abnormalities.

> Note that the definition of sick includes those patients with vague histories such as:

• Not eating well
• Unwilling to play
• Has less energy

> Erythrocyte, leukocyte, and platelet abnormalities should be evaluated prior to anesthesia for several important reasons:

• Anemic patients are more prone to tissue hypoxia, which increases the likelihood of anesthetic complications.
• Polycythemia most commonly results from dehydration (relative polycythemia). Dehydration may cause hypotension and may result in anesthetic complications especially when coupled with blood loss and the vasodilatory effects of many anesthetic agents.

• Elevated total protein and concentrated urine specific gravity are other laboratory abnormalities associated with dehydration.

• Leukocytosis may be associated with inflammation, stress, or excitement (physiologic leukocytosis).
• Leukopenic and neutropenic patients may have difficulty in mounting an effective anti-inflammatory response postoperatively.
• Thrombocytopenia is the most common bleeding disorder in veterinary medicine. Platelets must be evaluated in every pre-anesthetic test because the consequences of thrombocytopenia can be life threatening.

> Because it is an excellent screening tool, which provides a wealth of information at relatively low cost, we recommend pre-anesthesia hematology and chemistry for all surgical candidates regardless of age.

> Geriatric patients, both healthy and ill, are also prime candidates for laboratory testing. Annual screening is recommended for healthy dogs and cats over the age of 7.

• Blood profiling provides important clues to underlying often-unrecognized diseases and helps establish baseline data, nutritional, and vaccine recommendations.

• The minimum senior canine database includes the history (including behavior), physical exam, CBC, biochemical profile with electrolytes, and complete urinalysis.
• The minimum senior feline database includes the history (including behavior), physical exam, CBC, biochemical profile with electrolytes, complete urinalysis, and total T4.

• Aging is associated with an increased incidence of a variety of disease states which may be recognized first on the basis of abnormalities in the CBC, urinalysis, and/or chemistry profile. These include:

• Immune-mediated disorders
• Endocrinopathies such as diabetes mellitus, hyperadrenocorticism (Cushing’s disease), thyroid dysfunction, and hypoadrenocorticism (Addison's disease)
• Renal disease
• Hepatic disease
• Neoplasia

• Senior/geriatric laboratory profiling is both good medicine and good business.

• A recent AVMA study reported that 28.1% of US dogs and 25.4% of US cats were 8 years of age or older.

In-clinic versus Outside Laboratory

Advantages of in-clinic hematology capability include faster patient management, better pre-anesthesia management, and the minimization of artifacts caused by delayed analysis.

> Improved patient management results from earlier diagnosis and treatment.

• Clinicians can use in-house laboratory results to determine the patient’s health status (sick or well), create diagnostic and treatment plans, and provide written estimates for clients during the same office call.

> Client compliance increases when pre-anesthetic testing occurs in-house because the pre-anesthetic profile is performed the same day as anesthesia therefore minimizing client inconvenience.

> Pre-anesthetic testing should be performed immediately prior to anesthesia to properly evaluate patient status and adjust anesthetic regimes.

> Hematology samples should be analyzed as soon as possible to prevent artifacts created by exposure to anticoagulants and cell deterioration due to storage and shipment.

• Blood films should be prepared within 30 minutes of collection to avoid morphologic artifacts.
• Platelet counts should be performed as soon as possible after collection for optimal results.

Potential disadvantages of in-clinic hematology include slightly higher cost/sample, the potential for less complete quality control depending on the in-clinic technology, and limited expertise in microscopic assessment of blood films.

> Concerns regarding quality control can be minimized by:

• Running in-house controls on a daily basis and charting results to ensure that there is no instrument drift in the results.
• Frequently splitting samples and checking in-house results against those of a quality reference laboratory.
• Joining a national quality control survey such as that provided by the American Society of Clinical Pathologists.

> As long as in-house quality control is maintained, the slightly higher costs of in-house hematology can be easily justified on the basis of better service to the patient.

Communicating the Need for Hematology

Most clients understand that human diseases are usually diagnosed through testing. Make clients aware that you do not want to guess.

> Clients understand that doctors should base treatment decisions on diagnosis, not speculation.

Use simple terms and explain that blood tests are required to rule out common diseases people are familiar with like anemia, infection, diabetes, and kidney disease.

> Many clients are familiar with the term "CBC" and "chemistry panel" through medically oriented television shows.

> Explain that these tests are like puzzle pieces which doctors use to narrow the list of potential diseases (differential diagnosis).

Remember that "normal" results are good news to the client and not money wasted.

> "Normal" laboratory results are common and have great value.

> Laboratory testing is used to help rule out diseases as well as to help identify them!

Communicating the Results

Copy the laboratory results page to discuss your findings with clients.

> If results are abnormal, recommend treatment or additional diagnostics such as cytology, radiography, ultrasonography, endoscopy, etc.

> If results are normal, advise clients what diseases you have ruled out (i.e., diabetes, anemia, infection, kidney disease).

Provide more information by copying an article on the diagnosed disease from a textbook or other reference source. This reinforces your diagnostic efforts and provides treatment and prognostic information for the client.

The Economics of Laboratory Testing

Laboratory testing is an important profit center for veterinarians and should represent approximately 20% of average gross income according to the 2000 Veterinary Economics Best Practice Survey.

> The same survey reported $30 as the average charge for a CBC in the United States. Regional charges varied from a low of $21 in the South to $31 in the Northeast.

> Multiple surveys have shown that laboratory testing is relatively price insensitive when compared to regularly shopped items like vaccines, office calls, and flea and heartworm preventatives.

In-house testing is generally more expensive than outside laboratory testing. Consequently, veterinarians should charge a higher fee for tests performed in-house and justify the higher charges on the basis of faster, more customized service.