Trip Database Blog

Liberating the literature


January 2023

PICO search – it’s a special type of search

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)!

The number of systematic reviews in Trip

As part of the improvements to Trip we have had a special focus on systematic reviews (SRs), as these are a key element of EBM (and many recent posts on this blog relate to SRs). As it stands we are just shy of 500,000 (this figure includes a number of Health Technology Assessments). In addition to published SRs we also link to over 150,000 registered SRs – those planned and ongoing.

However, an important consideration of ours is that users may see a systematic review (at the top of the EBM pyramid) and suspend scepticism. So, we’re still working hard on a quality score for SRs. This is going well and I’d like to think it’ll make an appearance before the end of the year.

So, size is important but size with quality is even better.

Improving the quality of Trip

One of Trip’s virtues is being easy to use. Behind this ease is a hugely complex website, one that took over two years to re-code. As well as re-coding the website there were other problems that affected the quality of the site and we’re addressing these in a systematic manner. As we tick these off the ‘to do’ list, the site get stronger. Some recent work includes:

Systematic reviews (SRs)

We automatically grab new SRs from PubMed (and we recently improved the filter for identifying new SRs). However, we also obtain SRs from other sources and we have finished automating this process. So, now, every week we grab a whole batch of new SRs. Previously the ‘other sources’ was a manual process and was not regularly undertaken.

Ongoing clinical trials

Another system that was previously semi-manual and not undertaken regularly, was the import of ongoing clinical trials from This is now automated with new trials added weekly.

Broken links

The user interface – to alert us to a broken link – works well but the Trip process to fix these links was sub-optimal. We have now reworked that and it works really well. Less broken links = increased quality.

Our ‘to do’ list has been full of things like this – not major individual pieces of work but important aspects that might affect the performance of Trip. Each one ticked off means the less likely users are to have a poor experience – surely a good marker of quality.

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