Search terms

Once you have written your question (see ASK), use the PICO terms to design your search strategy.

Let’s look at an example based on one of the PICO questions used in ASK:

In [cats with naturally occurring chronic kidney disease] does [a renal prescription diet compared to normal diet] increase the [survival time] of affected cats?

The first step is to make a list of the key concepts to search for. In this example, the key concepts for the search strategy would be ‘cats’, ‘kidney disease’ and ‘diets’.


Note that the PICO and the search strategy are not the same thing – it is likely you will not search on all your PICO terms. For example, “Outcome” terms are often excluded from a search because they can be broad terms with many alternatives, meaning key articles may be missed if they are used.

The next step is to think of alternative terms for each concept. Think about alternative spellings for your terms (e.g. UK English / American English spellings); synonyms – different terms with the same meaning; colloquial phrases, and related terms which you would like included in your results.

Be as specific as possible, and where you are interested in a largish area (such as kidney disease), list all the more specific topics (like types of kidney disease) that you want to cover. See below for diagrams showing how you may organise your major subjects and keywords.

Chronic renal failure
Chronic renal disease
Chronic renal insufficiency
Chronic kidney failure
Chronic kidney disease
Chronic kidney insufficiency
Kidney diet
Renal diet
Prescription diet
Therapeutic diet