predisposition to disease. For example, cats with white fur may be at higher risk for developing squamous cell carcinoma; color dilution alopecia is more common in dogs with diluted coloring patterns, such as “blue” Dobermans.
3.4.4 Genotypic and Phenotypic Testing
Since pet‐specific care is about anticipating problems before they happen, typically through surveillance, screening tests are paramount to the process. The main categories of screening tests are based on phenotypic and genotypic assessment (see 3.11 Integrating Genotypic and Phenotypic Testing).
Genotypic tests assess a genetic mutation or marker to determine disease susceptibility. Such genetic tests measure either the presence of an actual genetic variant or genetic markers that appear to be associated with phenes. Genetic tests typically measure a specific variant associated with disease, while genomic tests may be used for more complex diseases in which there may be interactions among genes, and between genes and the environment; information may be assessed for disease susceptibility, prognosis, or likely response to therapy.
When it comes to genetic testing, there are many DNA tests that can be run, either individually or as part of a panel (http://bit.ly/2YWXBsc). For those that are only concerned with a single medical issue, individual genetic tests can be conducted. From a medical perspective, the most valuable information typically comes in the form of genetic panels in which multiple genetic tests are run at the same time (see 3.11 Integrating Genotypic and Phenotypic Testing). This will evaluate for dozens of medical conditions, as well as for certain traits (e.g., conformation, color, etc.). Sometimes specific breed profiles are requested, evaluating only conditions common in a specific breed, although with the new “chip” technologies, it is as inexpensive to run a complete panel with dozens or hundreds of tests as it is to run a handful of tests common in a specific breed. In almost all cases, it makes more sense (financial and otherwise) to run the complete profile rather than try to guess which tests might be most relevant. However, after running such a panel, it is necessary for the hospital team to determine which tests are actually relevant for each individual pet (see 3.8 Genetic Counseling).
Phenotypic tests are those that measure a detectable abnormality or variance from normal, rather than a genetic variant. This includes most of the tests we routinely use, such as hemograms, biochemical profiles, urinalysis, radiography, etc. For example, while genotypic tests can identify some variants of primary open‐angle glaucoma susceptibility at birth, phenotypic tests that rely on measurements of intraocular pressure (IOP) identify glaucoma when IOP increases above an established reference interval (range) for the breed.
Nutrigenomics will likely also play more of a role in healthcare with improved technology. There are several direct‐to‐consumer testing possibilities that purport to tell consumers how their eating habits could be associated with genetic predisposition and how sensitive they are to certain foods. Because of complicated environment–gene interactions, how individuals metabolize foods, and the role of the gut microbiome (see 4.6 Role of the Microbiome), this would be potentially complicated to interpret in pets.
3.4.5 History
Collecting relevant information from pet owners is critical to being able to provide truly personalized care for pets. Since pets spend much more time with their owners than with veterinary staff, pet owners must be engaged in the process and aware that such information sharing will ultimately benefit their pets.
Every hospital visit provides an opportunity to learn more about the pet, the pet owner, and how they interact with one another. In many cases, it is most efficient to use questionnaires to standardize the collection process (see 1.2 Providing a Lifetime of Care).
Important topics include understanding what other pets may co‐exist in the house, activities, and exposure, diets being fed, prescription and nonprescription medications being administered, etc.
It is also important to realize that preexisting conditions may be associated with increased risk for other disorders. For example, a pet diagnosed with Cushing's syndrome likely has an increased risk for diabetes mellitus. A pet with excessive skinfolds is likely predisposed to skinfold dermatitis. A pet with early radiographic evidence of hip dysplasia is more likely to develop osteoarthritis.
3.4.6 Counseling
The benefit for veterinary practices is that pet‐specific counseling is an important part of a personalized approach to healthcare, and research shows that hospitals that practice such client‐centric care typically have significant growth year on year, compared to practices that do not provide this type of service (see 10.11 The Financial Benefits of Pet‐Specific Medicine).
It is important to understand how early detection can influence future actions. An animal that is prone to cardiomyopathy based on genetic testing, family history or breed predisposition will potentially need regular cardiac monitoring, periodic radiographs, laboratory testing, and perhaps echocardiography, all before the condition ever becomes clinical. Once it becomes clinical, there will be pharmacological and dietary intervention, likely for the remainder of the pet's life. The client will also be more likely to want to comply if they have some documentation of susceptibility through DNA testing.
3.4.7 Checklists
Checklists have proven to be very beneficial in human medicine, where they have helped reduce medical errors, improved patient safety, enhanced teamwork, and ensured that steps were not missed (see 2.4 Checklists in Veterinary Practice). Without mandatory adverse event reporting, or morbidity and mortality investigations, it is difficult to tell how often medical mistakes occur in animals (see 8.14 Appropriate Handling of Medical Errors).
Checklists can also be used for more basic functions, such as history taking, presurgical and postsurgical checks, and even to ensure that certain topics are addressed in client educations (Figure 3.4.1).
Figure 3.4.1 Topics to be addressed in puppy/kitten client discussions.
3.4.8 Predicting Outcomes
Most traits/phenes recognized in veterinary practice, and those that cause the most problems, do not seem to fit neatly into Mendelian patterns of inheritance. When phenes such as hip dysplasia, allergies, epilepsy, diabetes mellitus, glaucoma, and colitis are considered, no easy answers are forthcoming. If the problem is presumed likely to be caused by more than one gene, it is labeled polygenic but most of the time, it is impossible to prove this without genotype testing. If a condition such as epilepsy is seen, which might affect more than one member of a breed line, it might be described as familial without knowing precisely how the trait is passed in that family. When a disorder appears to be more common in some breeds than in others, we call this a breed predisposition. Once again, in most instances the exact mode of inheritance is not known.
