How do we know what the best veterinary treatment for a horse is? *H&H VIP*

What is the best treatment for a horse with a tendon strain, or a pony with acute laminitis? The answer is that we don’t really know.

Every vet will have the necessary skills and knowledge to advise an owner about such conditions, but in most cases these treatments have never been studied in detail or assessed to determine how effective they really are.

To make the best clinical decisions and offer advice about diagnosis and treatments, a vet must take into account both an ever-increasing pool of scientific information and an owner’s values and preferences. Plus, the vet’s own clinical experience plays a major role in the decision-making.

While many vets attempt to monitor cases over time and build up knowledge about the efficacy of treatments, it is very difficult then to disseminate such information to the rest of the veterinary profession.

Trials and tribulations

The term “evidence-based medicine” was coined in human healthcare several decades ago to acknowledge the importance of the combination of relevant clinical research with the clinician’s expertise and experience. This approach has revolutionised clinical care in human medicine and is now being increasingly recognised as an important concept in veterinary medicine.

The recent upsurge of interest in this area has highlighted difficulties for vets in finding appropriate evidence. Despite a burgeoning amount of research into equine diseases, much has limited applicability to clinical practice in the real world.

Clinical evidence is generated from scientific research, but there are major problems associated with accumulating relevant scientific evidence relating to the treatment of equine diseases.

The most reliable evidence comes from treatment trials in horses affected by that disease. To be sure that a treatment really works, at least two groups of affected animals are needed. One group is given the treatment being studied, while the other group receives either an alternative treatment or none at all.

Such studies are known as controlled clinical trials.

“Controlled” refers to the horses receiving either the alternative treatment or none, the objective being to see if the group receiving the new treatment has a better outcome than this control group.

Ideally, the choice of group an individual horse is put into is randomised — made purely by chance (such as throwing a dice). In addition, trials should be “blinded”, meaning that those organising the trial and monitoring outcomes are not aware of which group certain horses are placed in.

Overcoming challenges

A major difficulty relates to the number of horses required to ensure an accurate and reliable outcome. To generate scientifically and statistically significant results, large numbers of cases with similar types and severities of disease are needed.

For example, while injury of the superficial digital flexor tendon is not usually associated with long-term lameness, there is a high risk of recurrent injury. Reinjury rates are 40-50% for sports horses and 50-60% for National Hunt racehorses, and even higher in Flat racehorses.

To prove that a new treatment is effective at halving the reinjury rate, two groups comprising at least 88 horses with similar severity of tendon damage would be necessary (88 being the optimum number, as determined by statistical analysis).

Despite the challenges, vets both in research institutes and in practice are making more attempts to generate clinical evidence. There is still a lack of convincing evidence, but recent studies have supplied us with important information about treating diseases including navicular syndrome, colic and arthritis.

Progress will be slow, but in time it will help drive up standards of care and improve the overall health and welfare of our horses.

Ref: Horse & Hound; 4 February 2016