Fat maps? Fat chance.

It comes to quite something when the best source that I can find for information about QOF analysis comes from GMTV. The big story is the "Fat Map" of the UK apparently produced by Dr Foster and sponsored by Roche. I say apparently but the actual map and report don't seem to feature on the web sites of either.

The data they appear to be using is the QOF obesity register size at PCT level for April 2007 which has been available on this site for ten months now. When you come down to the business rules level this is a measure of the number of patients over sixteen years old who have had a BMI measured (or technically weight measured and BMI calculated) between January 2006 and April 2007 and that BMI was greater than or equal to 30.

A BMI of 30 is not that high these days. For those of you who don't deal with BMIs on a daily basis (basically front line clinicians) Flickr hosts a rather wonderful range of illustrated BMI catagories.

The prevalence has then been calculated by dividing this number by the total registered patient population.

There are thus quite a number of confounding factors.

Firstly and probably most significantly is the enthusiasm of the GP practice for weighing lots of people. If people were not weighed they did not count. For instance a huge patient would not be counted as obese if they did not have a BMI recorded. Getting a high prevalence involved weighing everyone who came through the door who looked like they may have a BMI over 30. There was no incentive to weigh patients with a BMI of less than 30 so it was just not done much - GPs have a pretty good eye for rough BMIs. For this reason even if we could know how many BMIs were measured it would be a bad measure of the obesity prevalence due to the skewed population at the measurement level.

Secondly we have the dodgy denominator. Remember the definition above? It applied only to patients of 16 or over - which is fair enough. BMIs don't really work with children. However to get the prevalence it was divided by the whole population. So if you have a lot of under 16s then your obesity prevalence will tend to be diluted. Similarly if you have a generally aging population then your obesity levels would appear artificially high.

Finally we have areas such as coding which are probably pretty minor.

Wales in general seems to stick out on the map, or at least the bits I could see on news.sky.co.uk Now I don't know a lot about Wales other than what I see on Torchwood but it seems rather odd that the whole of Wales is high (from North to South) and that obesity starts right on the border. Was there a LES or other country specific reason for practices to be incentivised to check BMIs a lot?

So this is a pretty dubious set of statistics on a map. Could it be better? Well perhaps a little. I mentioned the problem of the dodgy denominator above. Is there a better figure that we could use? Certainly there is. Records 22 (recording of smoking status) applies to all patients over 15 and uses that population as its denominator. We could at least correct that error although practice rates of measurement will still be a significant factor. I will try to put the figures together and if Roche or anyone else want to sponsor it they are very welcome!

New Business Rules (v12) for 2008/9

We are now about a third of the way through the QOF year and I have just come back from my holidays to find that the new version of the QOF business rules has arrived. It is a no more gripping read than it was before and fortunately the changes are fairly minor this year. Most of the obvious changes seem to be in the area of smoking - both the clinical area and Records 22. This is the area that has received most attention this year - at least in terms of the coding areas. Just a reminder of what the guidance says:

The guidance has also been updated and in particular we would draw your attention to amendment to non-smokers and ex-smokers. Non-smokers should be recorded as such up until the age of 25 while the smoking status of ex-smokers should be for 3 years and only thereafter if their smoking status changes.

Now this has been implemented almost exactly as you see it here (for the one problem see below). Arguably there is a degree of ambiguity, and a missing bracket, in the way that the rule about three years is written but I am sure that the system suppliers can be relied on to implement it sanely. There is, however, an interesting anomaly in the way that the text above specifies the criteria. If a young man were never to have smoked by the age of 24 this would still have to be coded on an annual basis. If, however he had smoked when he was 15 and then became an ex smoker this would only have to be recorded from the ages of 18 - 20 and can then be stopped. Ex-teenage smokers are thus less work than those who have never smoked.

There are not that many young people in the smoking clinical indicators - they just don't feature in the chronic diseases that much with the possible exception of asthma and for asthmatics the smoking indicator only starts at age 20 (there is another indicator for younger asthmatics at Asthma 3). However around 80% of the practice population is also covered in Records 22, including all of the 18-25 year olds. For a typical practice this represents about 4742 patients. There are only 11 points here, around £1370 equivalent to just 58 pence for each patient in the "scoring zone" from 40-90%. It is likely that annually chasing young people who don't often attend the surgery to check that they have not started smoking will simply be uneconomic. That is not to say that nobody will do it though. For 2006/7 practices achieved 82% overall.

The recording of ex smokers for three years is however rather fragile. This may cause problems in the future although the effect should be limited this year. The problem is that the rules look only at the most recent codes and this could trip practices up. If a patient had given up smoking you could record this in years one, two and three. They would then not need a record again - ever. However if you recorded in years one, two and three - missed year four and then recorded again in year five another code would be needed in year six. The rules would see the code in year five and missed the previous year and not the three codes in the years before.

Now this is not really the fault of the rules writers. The structure of the rules is not that flexible and they have done their best within these limits. The rules have a very linear structure and there is no option for looping or iteration. The designers of QOF at the DH and the BMA are getting more ambitious with much more complex targets; the smoking rules are probably the most complex in the whole of the framework so far. Many people have big plans for new QOF areas in the future and it may be time to look at an overhaul of the way the rules are set and the systems that implement them. We are likely to see an increasing number of problems of this nature unless ambitions are reigned in a bit - and personally I don't see that happening.