Introduced over ten years ago, the PICO search is very popular with our users. However, it is frequently misunderstood. Yesterday we received an email from a user:

We are finding different results between advanced search and PICO search. We are using the same terms. Is this possible? Is there any way to solve it?

So, what’s going on? PICO search is not designed to be an exhaustive search, it is designed to find a small number of highly relevant results. Or, put it another way, it’s a very specific search not a sensitive one.

At the heart of the PICO search is something called contingency searching, which helps us deliver a specific search.  After the user enters their search term our first search is for all the PICO elements as title only searches. If there are too few results we then make the final search term entered a ‘title and text’ search and repeat the search and if that too has too few results we make the penultimate term a ‘title and text’ and we repeat that until we get a manageable number of results. All these repeated searches are done in the background; from a user’s perspective it’s a single search.

So, if you want lots of results use the default or advanced search. However, if you want a more focussed set of results use PICO (although the default search is pretty good as well)!