Individualize Veterinary Medicine with Baseline Data

The difference between working up “a” dog or “this” dog

Veterinarian caring for a dog

Our patients can’t talk, so we veterinarians must rely on an owner’s recount of their pet’s history, the physical exam and diagnostics to work up a patient. We encounter histories that range from nonexistent or sketchy to vague and everything in between. Sometimes, we get what we need but more often we do not.

The physical examination is the foundation of a patient workup. I would gamble that the average veterinarian has mad physical examination skills compared to his or her human physician counterpart. That’s because our examinations have to compensate for a lack of key information and communication. And to make things more interesting, our patients are frantic, tense, excited, angry, confused or all of the above.

All of this brings us to diagnostic testing—a consistent and reliable source of information. A practice management expert will tell you that you should derive at least 25% of your revenue from diagnostics. Like many vets, I shy away from matters of finance, but I can tell you that you will eventually lose your sanity if you are not using diagnostics in all your workups. Unless you are Dr. Doolittle and have found ways to communicate with your patients, you simply have to leverage the value of diagnostic testing.

Profiling chemistries, trending results and careful monitoring will take you from peeking at a snapshot of your patients to seeing a more dynamic picture—from looking at all dogs’ or cats’ reference intervals to focusing only on the specific reference data for the patient in front of you.

Individualizing diagnostics

A reference Interval (RI) is designed to put a diagnostic result into some sort of context by comparing a number to a larger population. This can be very helpful. When we derive RIs, we look at a large, presumably healthy population. From there, we plot all the results in a histogram, usually removing the top and bottom 2.5%, so that the range encompasses 95% of the population. While RIs can get more complex in their computation (results are rarely normally distributed and nonparametric analysis and other elaborate statistics are sometimes employed), they are designed to include the majority of a given population. In other words, they are designed to be broad, all-encompassing and general by nature. You have only to look at a Maltese next to a mastiff to know that using a single range for all dogs might not be appropriate.

Breed, gender, reproductive status, life-stage and lifestyle differences can all have a major impact on test results. A peak performing athlete and a couch potato have little in common in terms of muscle mass, so it’s not surprising that their “normal” creatine kinase levels might differ as well. Likewise, it appears that the hematocrit (HCT) in some larger breed dogs tends to be lower than in their smaller counterparts. So, when you see a Great Dane on the high end of the RI for HCT, this may be cause for concern. But did you know that most analytes are fairly consistent in health? And it’s a good thing, because it gives us the sensitivity to go from looking at all dogs to just one: the one you’re seeing right now.

In a recent article in the Journal of Veterinary Clinical Pathology, the authors revealed that all but three analytes should be assessed by individual-based reference intervals.1 Only glucose, triglycerides and phosphorus were found to be sufficiently robust to use population-based reference intervals. For every other analyte, it’s best to establish what is normal for an individual patient and then use that number as a baseline for future comparisons. And this is true for hematology as well as chemistries.

So how do you create a baseline for your patients? Test them in health. The first time can be the preanesthetic testing you were already going to do for spay or neuter surgery. Be sure to expand the preanesthetic profile to include a CBC, a full biochemical profile with electrolytes and a urinalysis. Not only will you have a solid baseline, but you’ll also get the added information for presurgical assessment to help ensure a smooth and eventless anesthetic event and recovery. The cost to perform these extra tests isn't significantly more, so you can even offer a special price for the bundle.

Getting to know your patients as individuals

Let’s use lipase to illustrate the point. The RI is broad for dogs: from 200–1800 U/L. It doesn’t indicate pancreatitis until you get a result that is 3 times (3X) greater than the upper end (>5400 U/L!). Fortunately, we only have to assume that upper end worst-case scenario when we don’t know anything about the dog. The same 3X rule applies for what is “normal” for that patient. So, if you know that this particular dog usually has a lipase value of 400 U/L, then anything over 1200 U/L may suggest pancreatitis, even though that value is well within the reference interval. Follow-up testing with a pancreas-specific lipase test pet-side (SNAP cPL Test) or at the reference laboratory (Spec cPL Test) might be warranted to help confirm or refute your suspicion. Without baseline data, you may have missed this early warning that the dog was at risk of developing clinical pancreatitis. You can advise the pet owner to avoid fatty treats, monitor more closely, and bring the dog in immediately if he goes off his food or vomits.

Annual baseline testing helps you perform smarter, more accurate diagnostics for your patients. It is the difference between caring for just any dog or the one right in front of you. Getting to really know and care for your patients is what makes you a great veterinarian. Trending your patients’ results is another way to help you get there.

Profiling chemistries, trending results and careful monitoring will take you from peeking at a snapshot of your patients to seeing a more dynamic picture—from looking at all dogs’ or cats’ reference intervals to focusing only on the specific reference data for the patient in front of you.

Michelle Frye, DVM, SM

Michelle Frye, DVM, SM
IDEXX Laboratories

Dr. Frye received her DVM from the University of Georgia and her master’s degree in infectious disease epidemiology, specializing in molecular genetic testing, from Harvard University. She completed her residency and fellowship at the Centers for Disease Control and Prevention, where she worked on field outbreaks and quality assurance for laboratory testing. Dr. Frye is the marketing manager for IDEXX Medical Affairs Department and manages the North American Advisory Board.

 

Reference

  1. Ruaux CG, Carney PC, Suchodolski JS, Steiner JM. Estimates of biological variation in routinely measured biochemical analytes in clinically healthy dogs. Vet Clin Pathol. 2012;41(4):541–7.