Tuesday, 14 September 2010

PICO questions

Since I referenced PICOs in my last blog I thought I'd mention them here as they offer a great structure to help us find evidence for intervention studies. It's all about asking a clear and concise question so that you can - hopefully - find a clear answer.

The P bit stands for the patient or problem you are concerned about.

Let's imagine a 50 year old lady who had a load of amalgams placed mainly when she was young. She's read that dentists crown patients' teeth when they've got big fillings in because it stops them from breaking and losing their teeth.

What's the P here? The P is a problem in a patient - in this case a patient with heavily restored teeth.

The I bit relates to the intervention. In this case the I is a crown (or an onlay). You want to know, as this lady's dentist, whether or not you should crown some of her teeth and - if you're going to - which ones. So you want to compare placing a crown against not placing a crown to know if the crown is better.

So C is your comparison or control. In this case that is a filling - either amalgam or composite. If all we looked at was the survival time of a crown, without comparing it to the filling, we wouldn't know whether the filling might last just as long - or even longer.

Finally O is the outcome or outcomes you're interested in. What matters to the patient in this case? She is probably worried about losing her teeth. So the bottom line will be - does placing a crown mean that she'll keep that tooth longer than if she had just left it with a filling?

Another outcome might also be which restoration has to be replaced most frequently, or what the long term cost is of each treatment. And an outcome that is often forgotten is whether there are any adverse effects: does the tooth die, does it fracture catastrophically so it has to be extracted, does one cause mouth cancer?

We usually decide on one main outcome that really interests us. In this case I'd go for whether or not the tooth was retained longer as without this information it's very difficult to decide whether one is more cost-effective, for example.

So the PICO question here would be:

For an adult patient with an MOD or larger restoration in a molar tooth (P) does a crown or onlay (I) rather than a composite or amalgam (C) result in the tooth being retained longer (O)?

So why do this? Well, if you're going to search for evidence one way or the other - even if it means asking an expert (even though they lie way down the bottom on the hierarchies of evidence) - it is important to have a clear question. From this you can create a search strategy to use with Medline or the Cochrane Library and in a short time you can identify any good papers that might help you answer your question.

For more on this have a look at the Centre for Evidence Based Dentistry website


  1. Do you have suggestions for a PICO question related to regeneration of new teeth with the use of stem cells? The problem is I'm trying to get my table clinic and PICO question to work hand-in-hand so I have less research since I'm currently working on both. I really like how you have explained how to construct a PICO question, but with mine I don't really have a comparison in order to make it work. Thank you.

  2. Hi there - and sorry for not replying sooner.

    I'm afraid I don't understand what you mean by table clinic - can you elaborate?

    Let me see if I understand your question: do stem cells help regenerate teeth? (correct me if I'm wrong).

    At this stage, since you're probably talking about lab work, the PICO framework may not help. PICO helps mostly to frame clinical problems but let's see if I can use the logic of PICO to help...if I'm not too late.

    The problem (P) is that we want to create new teeth. So search terms around this might be something like: (regenerate OR regeneration OR generate OR generation OR grow etc.) AND (teeth OR tooth OR dental OR odonto* etc.).

    The intervention (I) would be the use of stem cells so terms would revolve around those used for stem cells - I'm not up on that area of research so can't comment on what these may be. Perhaps simply 'stem cell'. (you can always try a thesaurus if you're stuck for different ways of saying something).

    Now, if you wanted to know if stem cells were better than an alternative at generating new teeth you would need terms for that comparison (C). It doesn't sound like you're at that stage so you can just ignore this.

    In terms of outcomes (O) we often don't use terms related to these in a search as there are often so many different ways of expressing outcomes and if you happen to miss the one a particular researcher used then you miss their paper. I think, given that you're doing some basic science research here, I would skip this.

    So in the end you may only use P and I. That's fine.

    Hope that's helpful and thanks for the comment :-)

  3. Thank you Dominic. Table clinic is something we have to do in dental hygiene school for the Florida Dental Hygiene Association Symposium. We come up with an idea (usually based from PICO) and compete for the #1 in the state. I think what you suggested did help, but since the research is so new (especially not approved in the states) that we decided to change our topic to burning mouth syndrome.

    That happens to be of course another complicated topic because the etiology of disease is often unknown, but there are a lot of possible local factors for disease.

    I like your blog and when I have time from school, I will certainly read up. I know it's a little different because you are a dentist, but the information is generally the same. :) Thank you for your help!