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What makes good evidence and how do you find it?

08 May 2019, at 9:30am

To make evidence-based decisions, it is important that we understand what good evidence is and how to find it

Veterinary professionals have to make clinical decisions according to their experience and expertise, based on the best available evidence. But how do they know what constitutes good evidence, and how do they find that evidence?

Every practitioner can get answers to both those questions in just three steps:

  1. Ask an answerable clinical question
  2. Find the available evidence to answer the question
  3. Critically appraise the evidence for validity

The joy of these steps is that anyone can attempt them once they know the techniques (which, hopefully, will be the case for you by the end of this article) and they can be approached in bite-sized chunks among the day-to-day workflow of a busy practice.

Identify your question

The opening step is to identify what you would like to find the evidence in relation to. It is possible to keep this loose and not narrow it down to a specific clinical question, but it is best to narrow it down when possible and it is likely to make the literature search (the second step) more effective.

The key aspect to maintain when coming up with your question is to word it in such a way that all relevant studies and articles will be captured in the search. One way to do this is to use a tool that breaks down the question into its constituent parts. An example of such a technique is the PICO method, which was covered in this column in the June 2018 issue of Veterinary Practice magazine. (PICO stands for patient/population, intervention, comparison/control, outcome.)

As an example, the question “In adult bitches does neutering versus not neutering reduce the risk of mammary tumours?” can be broken down into just its PICO elements: adult bitches; neutering; not neutering; mammary tumours.

It is important to note at this point that step one can also be approached the other way around: you can either start with a question and break it down or you can begin with the key components and construct a clinical question from there. Either way, the terms above are the starting point for step two, the literature search.

Search the literature

This is perhaps the trickiest step in the process as you need to convert those key elements of the clinical question into a list of search terms that is as exhaustive as possible. RCVS Knowledge has a handy toolkit that will show you exactly how to do this.

Once you have your search terms, you can plug these in to any number of databases, such as CAB Abstracts, PubMed and VetMed Resource. A combination of CAB Abstracts and one or more other databases is the most likely to return the vast majority of available evidence. Now comes the fun part: reading and appraising the evidence.

It is quite likely that certain studies returned by the search will stand out, but it is always good to read any introductions. Titles and abstracts aren’t always perfect descriptions of a study, and other papers may contain elements relevant to your question that aren’t immediately obvious.

Critically appraise the evidence

Having collated the papers you want to read in more detail, focus on the methods and findings, keeping a critical eye on signs of bias or alternative explanations for the results.

It is important to consider the type of study – different types offer different levels of evidence, and are more appropriate to certain clinical questions. It is also worth considering the quality of the methodology – see RCVS Knowledge Toolkits 3 to 11 for guidance and a checklist to tackle each type of study. Appraising is a skill unto itself, but one that anyone can learn.

So now you’ve found the best available evidence, what do you do with it? Add it to your knowledge repertoire and put it into practice.