As vets, we are always trying to find the best treatments for our patients. This often leads to us trying something relatively new. When considering new treatments, we need to think about what evidence there is. For drugs, that is usually relatively straightforward, since for a drug to get a veterinary licence it will already have undergone millions of pounds worth of trials and safety testing.
For a few drugs, we are lucky to have further clinical trials done by practitioners and specialists. One recent example is the “evaluation of pimobendan in dogs with cardiomegaly” (EPIC) study, which involved 360 dogs, half of which were given pimobendan and the other half a placebo. It was, according to the EPIC website, the largest veterinary cardiology study in history. The study sought to answer a key question: “Can pimobendan… delay the onset of CHF caused by MMVD?” and to determine “whether longterm administration of pimobendan could delay onset of CHF, cardiac-related death, or euthanasia”.
The study began in 2010 and ran through 2015; the EPIC website states that it “included investigators at 36 study centres in 11 nations across 4 continents. Investigators were held to rigorous scientific standards, and an independent team compiled and reported the findings”.
It is not the top of the evidence hierarchy as no one is likely to repeat it enough times to allow a systematic review of all those trials, but it is probably as good as it gets
This size of trial is rare in veterinary medicine but would still be considered quite small in human medicine, in terms of patient numbers. However, I think we can all now take on board its findings and prescribe accordingly.
The RCVS Knowledge site has lots of useful resources for helping vets to evaluate evidence. One important concept is the hierarchy of evidence, which lists opinion as the weakest evidence and systematic review of studies as the strongest.
The full list runs: systematic review > meta-analysis > randomised controlled trial > cohort study > case control study > case series > case report > opinion.
For the EPIC study, we have a veterinary licensed drug with a large prospective randomised, controlled trial undertaken for a new clinical indication of that drug. It is not the top of the evidence hierarchy as no one is likely to repeat it enough times to allow a systematic review of all those trials, but it is probably as good as it gets.
How to evaluate the evidence, and what evidence there is for surgical techniques and other interventions, is not so clear for us in practice. For example, for those of us not doing the latest cruciate technique but referring them on, what is the level of evidence for these different techniques? Maybe a case series at best. With some of them being pretty much copyrighted, it is difficult to imagine a case control study being done.
This was brought into focus for me when doing stem cell treatment for arthritis. We had done a small number of cases in our practice and had good results. We had received a good presentation (delivered by someone with a relevant PhD) from the lab that grows the stem cells, with what seemed to be a good level of evidence up to a small case series. However, when seeking pre-authorisation from an otherwise reliable pet insurance company, we were told that they would not cover it as “there was not enough evidence” for the procedure.
Now there is nothing more guaranteed to put the hackles up on a vet in practice than to be told by a distant “number cruncher” that we are not doing our clinical work in the way they would like it; another example of this is insurers telling us where to refer cases. It seemed a slightly illogical response when they would no doubt pay out for surgical interventions with much less evidence.
So once again it appeared that as a vet in practice, I was having my clinical decision making further complicated by external factors.
Should insurers insist on a minimum of a case controlled study before paying out? Should vets not try new techniques until the specialists have validated them? Or should we follow famous veterinary ophthalmologist Shelia Crispin’s comment on using phenol in Boxer ulcers: “I’ll stop using it when it stops working”?
