Urinary cystatin C prognostic marker in acute kidney injury

By Sally Robertson, B.Sc.Mar 1 2013

Urinary cystatin C (uCysC) level may be a useful biomarker for discriminating between prerenal and intrinsic acute kidney injury (AKI), report researchers.

"Our findings may assist physicians when making therapeutic decisions regarding patients with AKI," remark Jin Kuk Kim (Soonchunhyang University Hospital, Bucheon, Korea) and colleagues.

"In the vast majority of patients with this medical condition, renal function is reversible if treated promptly," says the team. "So, accurate and rapid diagnosis to discriminate prerenal from intrinsic AKI is required."

In a study of 213 patients presenting with acute kidney disease, uCysC levels were significantly increased among 127 (59.6%) individuals who had intrinsic AKI compared with among 86 (40.4%) who had prerenal AKI, at 2.20 versus 0.00 mg/dL. In addition, the ratio of uCysC to urinary creatinine (uCysC/uCr) was significantly increased in the intrinsic versus prerenal AKI patients, at 0.03 versus 0.00.

As reported in Nephrology, the team performed receiver-operator characteristic curve analysis to test the discriminative ability of the two biomarkers in diagnosing intrinsic AKI, and compared this with the discriminative ability of fractional excretion of sodium (FENa), currently the most widely used marker for differentiating between the two stages of disease.

The team reports that both uCysC and UCysC/uCr showed a strong ability to diagnose intrinsic AKI, with areas under the operating curve (AUCs) of 0.80 and 0.82, respectively, whereas FENa showed a poor discriminative ability, with a low AUC value of 0.64.

Using Acute Kidney Injury Network criteria, the researchers defined and classified disease stage among the individuals with intrinsic AKI, of whom 39 (37.7%) had stage 1, 37 (29.1%) stage 2, and 51 (40.2%) stage 3 disease.

Analysis of these subgroups showed that uCysC concentration increased with the severity of intrinsic AKI, at 2.66, 3.89, and 5.06 mg/dL for stage 1, 2, and 3 of intrinsic AKI.

The uCysC/uCr also increased with advancing disease stage, although this did not reach significance. However, in multivariate analysis, the uCysC/uCr ratio was significantly predictive for in-hospital mortality among the patients, with an AUC of 0.75.

"Urinary cystatin C may be of clinical value in patients with AKI," write Kim and team.

"Further studies that include greater numbers of patients and multiple centers are necessary to confirm these findings," they conclude.

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