On this site there have been several thoughtful posts (e.g. by Dr. Atwood and by Dr. Novella), and subsequently much heated commentary, on the distinction between Evidence-Based Medicine (EBM) and Science-Based Medicine (SBM). I agree wholeheartedly with the position that the two are not mutually exclusive, and that SBM is essentially EBM as it should be practiced, with a comprehensive consideration of all relevant evidence, including the subject of plausibility. As a practicing veterinarian, and an officer of the Evidence-Based Veterinary Medicine Association (EBVMA), I am keenly interested in bringing to my profession a greater reliance on high quality research evidence and sound scientific judgment, and reducing the reliance on individual practitioner intuition and experience in making clinical decisions. However, those of us in veterinary medicine face some special challenges which make the subtle but important distinction between EBM and SBM especially salient. 

Where’s the Evidence?

The first of these challenges is the paucity of high quality clinical research evidence. As an example, in his 2007 book Snake Oil Science, R. Barker Bausell examined the research evidence concerning the use of glucosamine as a treatment for osteoarthritis in humans. He was able to analyze the strengths and weaknesses of a Cochrane Review which included 20 studies with 2570 patients (the most recent revision of this review includes 25 studies with 4963 patients), a NEJM study with 1583 patients, and an Annals of Internal Medicine study with 222 patients treated for two years. His conclusion was that the intervention was not more effective than placebo.

I recently did a targeted search of the PubMed literature database for a brief evidence-based medicine feature on the subject of glucosamine and chondroitin as treatment for osteoarthritis in dogs, currently in press at the Journal of the American Veterinary Medical Association. A search of the terms “glucosamine,” “arthritis,” and “dog” yielded eight references, of which three were relevant (a more comprehensive search strategy yielded sixteen references, but only the same three were relevant to the clinical question). The three useful references included two clinical trials involving a total of 113 dogs and each lasting about 2 months, and a systematic review of treatments for canine osteoarthritis which evaluated one of these two clinical studies. Predictably, the larger, better designed trial with objective measurement criteria showed no benefit of glucosamine, while the smaller, less well-controlled trial with only subjective criteria and a 23% dropout rate in the glucosamine group showed some benefit at some assessment points.

Where’s the Money?

Glucosamine is an extremely popular, and profitable, supplement routinely recommended by veterinarians and administered by owners to their geriatric dogs. Yet the clinical trial evidence concerning its effects is nearly non-existent. The depth of the evidence is no better for many, many routine clinical interventions in veterinary medicine. The primary reason for this is simple: money. 

Obviously, the health of companion animals is not as high a societal priority as human health. Many countries have little or no formal companion animal medicine at all, of course, much less high quality, evidence-based pet medicine. And even in the developed world, the absolute size of the veterinary medical profession and associated industries is dwarfed by that of the human medical industry. 

In the United States, surveys show that most dog and cat owners have come to consider their pets to be members of their family, and their willingness to pay for veterinary care has increased along with this shift in attitude. The same appears to be the case in Europe and other developed nations. This has allowed the quality and technological sophistication of veterinary care to increase. 

Pharmaceutical companies have followed this trend, increasing their financial investment in their own internal research activities, as well as funding the lion’s share of companion animal health research generally (with all the ethical and practical problems that creates). Pfizer, the largest fish in the “Big Pharma” pond, claims to spend $300 million annually on veterinary research globally, for both companion and agricultural animals. However, the company is expected to spend $9-$9.6 billion this year on its human research and development. The same pattern is true of government research spending. Veterinary medicine will always be the poor stepchild of medicine, and we cannot expect to have anything close to the quantity or quality of research evidence available to MDs trying to practice evidence-based medicine. 

A Pack of Lone Wolves?

Another barrier to effective utilization of research evidence in veterinary medicine may be demographic and cultural. In the United States, the average veterinary practice has fewer than three veterinarians, and between one-third and one-half of veterinarians are self-employed practice owners. And most companion animal veterinarians are general practitioners, only about 10-15% of practicing vets being board-certified, with the extended academic training and, hopefully, greater awareness of and respect for research evidence that might be expected to come from this training.

As a profession, we veterinarians tend to be entrepreneurial, self-reliant, and independent. This contributes to a reluctance to let anyone tell us what to do, which may be how veterinarians perceive the position of evidence-based medicine. There is no solid data on the subject (though I am involved in a survey study which will hopefully provide some soon), but in discussions with colleagues I have sensed a great deal of anxiety about the notion of “cookbook medicine” which disdains the hard-won wisdom and experience of the individual clinician. Veterinarians are reluctant to accept the idea that there may be broadly applicable standards of care they ought to adhere to, even if their personal judgment conflicts with the evidence for these.

Undoubtedly, our colleagues in human medicine share a similar temperament and similar sorts of anxieties about “cookbook medicine”. However, these may be tempered to some extent by more widespread advanced training, more structured and supervised practice environments, and greater assessment and monitoring of outcomes, which may partially explain the greater acceptance of EBM in the human medical profession. And though the case of Dr. Rolando Arafiles, Jr. illustrates the weaknesses in the systems for monitoring physician behavior, I think it is clear that the influence of government regulation, and the threat of litigation, give the concept of adhering to a recognized medical standard of care far greater teeth in the field of human medicine than it has in veterinary medicine.


So how does this relate to the difference between SBM and EBM? Well, traditionally the scarcity of clinical trial evidence has led veterinarians to practice primarily opinion-based medicine. Personal experience and intuition and the opinions of individual experts or mentors are the predominant foundations for clinical decision-making. There is little or no outcome assessment, so veterinarians must rely on their own clinical experience to judge whether their practices are effective. 

The negative consequences of these strategies are many. There is dramatic inconsistency in the diagnosis and treatment of even common diseases. I routinely have to explain to my clients that if they ask ten vets a question, they are likely to get seven or eight different answers. You can imagine how frustrating this is for them, and how little confidence it inspires in our expertise.

OBM Leads Kids to the Hard Stuff, FBM!

As most readers of this blog likely already know, there are many reasons why individual judgment is an unreliable guide to the true efficacy of a medical intervention, and why we should be reticent to entirely trust our own intuitions and experience. But opinion-based medicine is also a “gateway drug” to faith-based medicine, otherwise known as complementary or alternative medicine. If you are accustomed to judging the safety and efficacy of interventions on the basis of the cases you have seen personally or the opinions of “experts,” you are more likely to be persuaded by the individual experiences of clinicians promoting and alternative practice, and more likely to think that giving it a try yourself is the most reliable way to know if it really works or not. 

The Internet abounds with holistic veterinarians who claim they started their careers as scientific, skeptical doctors but that their frustration with the limitations of mainstream medicine and the problems they could not solve led them to experiment with, and ultimately become promoters of, faith-based miracle therapies of every kind that share no theoretical or practical features in common other than being validated primarily by testimonial and not consistent with scientific knowledge or evidence. 

Tooth Fairy Science exists in veterinary medicine, but it is less of a problem than the simple lack of research evidence and the consequent reliance on even less trustworthy forms of evidence. So veterinary medicine needs a science-based approach even more desperately than human medicine because we have so little clinical trial evidence to rely on, and so few resources to generate more and better evidence. The tragedy of money and talent wasted on studying therapies that have vitalist theoretical foundations inconsistent with established scientific knowledge is even more poignant in the relatively impoverished world of companion animal medical research. Plausibility must play an important role in deciding how we allocate the scarce resources we have in order to maximize the useful information we can generate, and the subsequent clinical benefits for our patients.

Towards a One Health Approach

Veterinarians must also take advantage of the evidence that our colleagues in human medicine have generated for us. There are serious dangers in extrapolating research evidence across species, of course, but we cannot afford to entirely ignore the wealth of human medical research that is relevant to our patients. Examined cautiously and judiciously, this data can help us target our own research efforts more efficiently. Just as animal models have an important role, despite their limitations, in human health research, so human clinical research can inform veterinary medicine. As clinicians, we can make more science-based decisions, even when relevant veterinary research is lacking, if we are aware of the research in humans that already exists on the conditions and interventions we are considering. 

If glucosamine is shown to be no more than a placebo after years of research in thousands of people, how much money and effort should we invest in studying its effects in dogs? And how strongly should we promote it to our clients, the vast majority of whom must pay for their pet’s care out of pocket, without insurance coverage, and who commonly must eschew needed care or even euthanize their companions for want of money to pay medical costs?

A Worthy Goal

There has been a steady growth in the quality and sophistication of care available to companion animals in the last several decades, and I am hopeful that this will continue. But I believe the interests of our patients and clients will be best served if the care we provide is as soundly science-based as possible. And while I think evidence-based medicine can become the standard in the veterinary field, with beneficial effects on the quality of the care we provide, we need the additional features of the science-based medicine approach even more than our MD colleagues: a respect for the importance of plausibility in allocating research resources and an understanding of the need to integrate all relevant evidence when making clinical decisions about interventions in the face of a scarcity of high quality clinical trial research. 

Despite all the histrionic accusations of some alternative medicine advocates about mainstream veterinarians being tools of the pharmaceutical industry or reluctant to accept unconventional approaches only out of closed-minded prejudice or a fear for our income, the reality is that we care deeply for our patients and want to provide them with the best care we can. I truly believe, and I hope the profession as a whole will come to accept, that science-based medicine is far more likely to help us do so than the opinion-based medicine we have traditionally relied on.

Posted by Brennen McKenzie

Dr. McKenzie has always pursued a wide range of interests both within and outside of veterinary medicine. After completing a bachelor’s degree with majors in English Literature and Biology at the University of California at Santa Cruz, he followed the dream of becoming a primatologist. He obtained a Master’s in Physiology and Animal Behavior and worked for several years in environmental and behavioral enrichment for captive primates. Switching gears, Dr. McKenzie then attended the School of Veterinary Medicine at the University of Pennsylvania and began working as a small animal general practice veterinarian. In the course of trying to improve his knowledge and better educate his clients, he discovered evidence-based veterinary medicine, and he has served as President of the Evidence-Based Veterinary Medicine Association. This has led to numerous opportunities for speaking to veterinarians and the general public about evidence-based veterinary medicine and some of its ideological competitors. Dr. McKenzie has also reached out to the public through SkeptVet Blog, his contributions to the Science-Based Medicine Blog, and media interviews on veterinary medical topics. While working as a practitioner, speaking, and writing, Dr. McKenzie has continued to pursue post-graduate training and completed his MSc in Epidemiology at the London School of Hygiene and Tropical Medicine in 2015. In his sparse free time, Dr. McKenzie enjoys reading, hiking, playing his mandolin, travelling with his family, and sitting on the couch with his dogs watching the hummingbirds and woodpeckers outside his living room window.