Tuesday, 14 September 2010
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