4. How to construct a good EBVM question?

4.3. C – Comparator: comparison or control

4.3 C – Comparator: comparison or control

Now that you have defined your population and intervention of interest, you need to consider your choices (i.e. what the intervention will be compared to).

It is important to realise that any intervention needs to be considered at the same time as a comparator, as without a comparison it is difficult to evaluate the impact of the particular treatment, prognostic factor or exposure you are interested in.

Table 3: Examples of questions with comparators


Which diet is best to feed cats with chronic renal disease?

Not feeding a renal prescription diet

Which diagnostic test is most reliable for diagnosing fascioliasis in lactating dairy cattle?


Does sex affect survival in flat-coat retrievers with cutaneous lymphoma?

Being female

Are the risks of inhalational induction of general anaesthesia higher compared to injectable induction ferrets under different protocols?

General anaesthesia induction by inhalational agent

Are cardiac disorders in Welsh Section A mountain ponies more prevalent than other breeds?

Being any other breed of horse