Thursday, 3 October 2013

Ouch! Why is it so hard to assess children's pain?

The simple answer it is difficult to assess pain full stop, because pain is by definition subjective, the classic definition being that it is whatever the experiencing person says it is.  With children of course there is the added complication of developmental issues, in particular the inability to verbalise pain.

To get round this, there are a large number of different pain assessment tools and scales, ranging in complexity from a straight line with no pain at one end and the worst imaginable pain at the other; to quite sophisticated behavioural tools, which try to identify behaviours associated with pain.  The problem remains though; how do you know when someone who can't verbalise pain is in pain, and how do you know your treatment is working?

A new study has looked at two tools that are fairly commonly used, a 'faces' scale and a colour intensity scale.  The first has faces that reflect differing degrees of discomfort; the second a graduated colour scale, where more intense colour is associated with greater pain.  In my travels around hospitals in the UK, I have to say that I see these scales a lot, but I rarely see them actually used.  Never mind lets press on with the study.

They looked at the reliability and validity of these tools in children aged between 4 and 17 years in the United States who had painful and non-painful conditions; and compared the two tools.  When you are assessing how useful tools such as this are, there are two key things that people look for:
  1. Validity - is it actually measuring what you think it is (in this case is it measuring pain, or might it be measuring something else, such as mood?)
  2. Reliability - how consistent is it, in other words if you measured the same thing twice at the same time, would you get the same answer?
They actually did some quite sophisticated tests here, and found that overall the tools seemed to work quite well.  However, there is a but..

Firstly, the children were quite old; and there was least agreement between the tools in the youngest age-group, which is the very children in which it is hardest to measure pain.  Secondly, validity is context specific.  Just because it works with these children in this place at this time, it does not mean it is going to work elsewhere.  Watch for this one, the famous 'validated tool' which people talk about without often knowing the circumstances of the validation.  For example, a tool validated among old people in New York is not likely to be valid for children in Bolton.  You may think this sounds far fetched (and it is a bit) but I have seen similar claims made.  Lastly just because two tools agree, it doesn't make them right - they could both be wrong.  Often people refer to a 'gold standard' measure and compare a new measure to this, but even then there can be problems, for example the existing standard may itself not be very good.  Everyone 'agreed' about banking 5 years ago - it is just a shame that they were all wrong.

For parents my suggestion is to know your child's pain behaviours, and make sure that when you are with healthcare professionals you make them know that you know!

Tsze (2013) validation of self-report pain scales in children.  Pediatrics 132 e971-979