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CKD formula switch 'would decrease GP workload'

GPs could be treating hundreds of thousands of patients with chronic kidney disease unnecessarily because of flaws in the formula used to calculate eGFR, a new UK study concludes.

Researchers calculated that switching from the MDRD4 calculation currently used by most laboratories could reduce the number of patients diagnosed with stages 3 to 5 CKD by as much as 12%.

Analysis of results of more than 200,000 patients whose serum creatinine levels were examined at a large Scottish laboratory found use of CKD-EPI formula rather than MDRD4 cut prevalence of stages 3 to 5 CKD from 5.63% to 4.94%.

Switching formula would reduce the expected number of patients across the UK with moderate or severe CKD by around 400,000, the study found, with the researchers saying it could ease GP workload or allow them to focus on more severe cases.

Overall, the study found that 17,014 of patients tested were reclassified to a milder stage of CKD – 5.8% of the entire adult population. And 67% of those reclassified to milder stages were women, with a mean age of 50 years.

The researchers, whose study was published in QJM this week, admitted further assessment of the CKD-EPI formula was needed particularly in older women, a small number of whom were reclassified to more severe stages of the disease.

Study leader Dr Mark MacGregor, consultant nephrologist at Crosshouse Hospital, Kilmarnock, said: ‘[Switching formula] would reduce GP workload, or perhaps more accurately allow workload to be targeted at patients who need it most.'

‘The reduction in CKD prevalence is mostly because of reclassification of stage 3A to stage 2, which is not monitored in the QOF. Other studies have shown reclassified patients have a low risk of cardiovascular events – so reclassification is appropriate.'

Dr Donal O'Donoghue, the Department of Health's kidney tsar, said there were discussions about switching to the CKD-EPI formula but any change would have to minimise disruption to GPs.

He said: ‘There are international guidelines due in January and we have advised NICE that its CKD guidance needs revisiting. The time to consider this is after it has been debated by NICE.'

Dr Chris Jenkins, a GP in Stockwell, South West London, said: ‘On current criteria, more patients than we might expect – especially elderly ones – come up with a diagnosis of CKD. If this reduces the diagnosis in elderly patients that might be closer to what we clinically feel is appropriate.'

Q J Med 2011; 104: 1045–53

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