Extra kidney test could improve risk stratification

Testing for the protein cystatin C in addition to current markers of kidney disease more accurately predicts disease progression and death, research shows.

Kidney: current tests may misjudge the risk of disease (Photograph: SPL)
Kidney: current tests may misjudge the risk of disease (Photograph: SPL)

Researchers led by Dr Carmen Peralta of the San Francisco VA Medical Center, US, said the findings of their study would allow more precise diagnosis of chronic kidney disease (CKD) and better risk stratification.

NICE recommends albumin-to-creatinine ratio (ACR) be used as the primary diagnostic measure to identify CKD, with protein-to-creatinine ratio used as a secondary measure.

But researchers said these methods may misclassify staging of CKD because creatinine levels can vary, depending on muscle mass, age and race.

Cystatin C has previously been suggested as a potential predictor of cardiovascular events, but trials have yet to assess the use of these three markers together.

The researchers studied data from 26,643 adults divided into eight groups by eGFR. Patients were then followed from January 2003 to June 2010, and researchers tracked cases of all-cause mortality and incident end-stage renal disease as primary outcomes.

Among these groups, 2,904 patients were classified as having CKD based on creatinine-GFR.

Of the remainder initially not diagnosed with CKD, 3,863 (one in six) subsequently had CKD detected by ACR, cystatin C, or both.

Adding cystatin C to the initial risk scheme improved the predictive value of the classification. It meant that those re-assigned to a higher risk group had a three-fold higher risk of death than those reclassified to a lower risk group.

The authors said the findings suggested 'adding cystatin C to creatinine and albuminuria for risk prediction can more accurately reclassify persons and can distinguish important prognostic differences'.

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