Testing for albuminuria in patients with chronic kidney disease may mean that around one in six patients with significant proteinuria are being missed, according to a UK study.
NICE guidance recommends albumin-creatinine ratio (ACR) testing rather than total protein-creatinine ratio (PCR) in CKD.
The guidance was reinforced in March last year when the Department of Health wrote to GPs, PCTs and hospital laboratories insisting that ACR was the preferred test, two months after a Pulse survey found many PCTs were refusing to abandon the cheaper PCR test.
A retrospective study, presented at the joint British Renal Society and Renal Association conference in Manchester last week, assessed patient outcomes in 5,600 patients attending a hospital renal clinic between 1999 and 2008.
In patients with significant proteinuria – as defined in the NICE and SIGN guidance as a PCR above 100 mg/mmol or ACR above 70mg/mmol – a subgroup of 16% would be labelled as having significant proteinuria if PCR was measured but not if ACR was used.
Study leader Dr Shona Methven, honorary research fellow in cardiovascular and medical sciences at the University of Glasgow, said: ‘Screening with ACR alone will fail to identify 16% of patients who would be identified by PCR. This subgroup is at higher risk of death and renal outcomes than those with low proteinuria and merit identification.’
Dr Mark MacGregor, consultant nephrologist at the Crosshouse Hospital in Kilmarnock who also worked on the study told Pulse this was equivalent to 127,000 patients in the UK: ‘This subgroup of patients had the worst mortality outcomes, and had renal outcomes as bad as patients with both raised ACR and PCR.’
He added: ‘We recommend using PCR rather than ACR in patients with non-diabetic kidney disease, given that it is a cheaper test and has stronger evidence to support its use.’
A NICE spokesperson said: ‘Our guidance does not completely reject the PCR test. We have stated that there may be clinical reasons to use PCR in addition to ACR, particularly for quantification and monitoring of higher levels of proteinuria.’
Dr Donal O’Donoghue, the Department of Health’s national clinical director for kidney care and consultant renal physician at Salford Royal Hospitals Foundation Trust, told Pulse the ACR test was not perfect.
But he added: ‘I don’t think it’s valid to extrapolate from a secondary care cohort to a general population.’
ACR testing ‘misses one in six’ with significant proteinuria