• Zhongheng Zhang, Baolong Lu, Xiaoyan Sheng, and Ni Jin.
• Department of Critical Care Medicine, Jinhua Municipal Central Hospital, Zhejiang, People's Republic of China. zh_zhang1984@hotmail.com
• Am. J. Kidney Dis. 2011 Sep 1;58(3):356-65.

BackgroundCystatin C (CysC) has been proposed as a filtration marker for the early detection of acute kidney injury (AKI); however, a wide range of its predictive accuracy has been reported.Study DesignMeta-analysis of diagnostic test studies.Setting & PopulationVarious clinical settings of AKI, including patients after cardiac surgery, pediatric patients, and critically ill patients.Selection CriteriaComputerized search of PubMed, Current Contents, CINAHL, and EMBASE from inception until November 15, 2010, was performed to identify potentially relevant articles. Inclusion criteria were studies investigating the diagnostic accuracy of CysC level to predict AKI. There were no language restrictions in the search.Index TestsIncreasing or increased serum CysC level or urinary CysC excretion.Reference TestsThe outcome was the development of AKI, primarily based on serum creatinine level (definition varied across studies).ResultsWe analyzed data from 19 studies and 11 countries involving 3,336 patients. Of these studies, 13 could be included in the meta-analysis. Across all settings, the diagnostic OR for serum CysC level to predict AKI was 27.7 (95% CI, 12.8-59.8), with sensitivity and specificity of 0.86 and 0.82, respectively. The area under the receiver operating characteristic curve (AUROC) of serum CysC levelto predict AKI was 0.87 (95% CI, 0.81-0.93). In an analysis excluding studies that did not clearly define the measurement time point, early serum CysC (within 24 hours after renal insult or intensive care unit admission) remained of diagnostic value. For the diagnostic value of urinary CysC excretion, the diagnostic OR was 3.10 (95% CI, 2.00-4.81), with sensitivity and specificity of0.61 and 0.67, respectively. TheAUROC of urinary CysC excretion to predict AKI was 0.67 (95% CI, 0.63-0.71) [corrected].LimitationsVariation in criteria for definitions of index and reference tests, absence of measured glomerular filtration rate in most studies.ConclusionSerum CysC appears to be a good biomarker in the prediction of AKI, whereas urinary CysC excretion has only moderate diagnostic value.Copyright © 2011 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

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