Happy Prevalence Day!

Those of us whose day has not be entirely filled with the opening of cards it is also national prevalence day. Although the computers will not do the actual calculation for another month today is the day that is taken as a baseline for all of the prevalence calculations. My thoughts drift back a year to a nursing home in London.

Before I explain why I think this way I should probably explain the significance of prevalence. When the contract was first presented the value of points to a practice depended solely on the number of patients (or at least notional Carr-Hill patients). There was some fuss at time, not least pointing out that this was a disincentive to diagnose as the targets would be harder for the same amount of money. Thus an adjustment was put in. It could not be make the value of a point directly proportional to the prevalence as this would basically be a return to item of service payments. In the end the value of the point was proportional to the square root of the prevalence.

There was one other factor which was largely ignored at the time. It was that any practice with a prevalence below 5% of the prevalence of the maximum was adjusted to have exactly that 5% prevalence. Those who want more detail can read the full guide.

This is where the Nightingale House practice comes in. It is a small practice attached to a nursing home and, as such, had a lot of patients with mental health problems - in fact a huge 35.4% of their patients had severe and enduring mental health problems. This was not entirely surprising with their particular population although this is vastly higher than the national average of 0.6%

Unfortunately, and I must emphasise again through no fault of the practice, this made chaos of the prevalence formula. 5% of 35.4 is 1.77 and 97% of practices had a prevalence of less 1.77%. The upshot was that the vast majority of practices were standardised to the same prevalence and all differentiation was lost. This could amount to several thousands of pounds in difference. Practices with low prevalence gained, most practices with high prevalence lost and the square root ensured that even Nightingale House got paid less per patient than anyone.

Mental health was the most prominent example but there is a similar, if smaller effect in stroke, thyroid disease and LVD. The rules are different for mental health this year as well so we shall see if the QOF payment of every GP in England still depend on a nursing home in London.


Anonymous said...

here is the link for the full guide of the ADPF


- at... Those who want more detail can read the full guide.

Anonymous said...

Is it possible for the website to provide details of what the 5% minimum prevalence was for each clinical domain in each country.

It would be useful to know when prevalences are standardised to the same level causing differentiation to be lost as a result of practices with exceptionally high prevalences.

Gavin Jamie said...

Link corrected. Thanks.

I have put the threshold tables on the site now.