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Why the prevalence formula is so unfair

I wonder if I might help my colleagues to understand the unfairness of the prevalence formula with the following worked examples.

Prevalence payment calculation

5,891 = average practice size

NP = national prevalence

P = practice prevalence

PF = prevalence factor = sq root of P


Consider a quiet university four-partner practice

with 6,000 patients:

100 diabetics, achieve 80 points

NP 3 per cent P 1.67 per cent

So, PF = 0.75

0.75 x 80 x 75 x 6,000 = £4,583


Now consider a busy urban four-partner practice

of 8,000 patients:

300 diabetics, achieve 80 points

NP 3 per cent P 3.75 per cent

So, PF = 1.12

1.12 x 80 x 75 x 8,000 = £9,125


This pays less than twice as much for three times as much work! I can't see how this is either equitable or acceptable. We are not dealing with insurance-based reactive medicine here, it is actual clinical work as recorded by observable events.

If we use just the ratio P instead of square rooting it:


0.557 x xxxx = £3,403

1.25 x xxxx = £10,185

Still not quite three times as much pay but it reflects the workload better and would be more acceptable.

Dr John Fitton


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