title: Cystatin C in prediction of acute kidney injury: a systemic review and meta-analysis.
abstract: BACKGROUND
  Cystatin 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.
  
  
  METHODS
  Meta-analysis of diagnostic test studies.
  
  
  METHODS
  Various clinical settings of AKI, including patients after cardiac surgery, pediatric patients, and critically ill patients.
  
  
  METHODS
  Computerized 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.
  
  
  METHODS
  Increasing or increased serum CysC level or urinary CysC excretion.
  
  
  METHODS
  The outcome was the development of AKI, primarily based on serum creatinine level (definition varied across studies).
  
  
  RESULTS
  We 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].
  
  
  CONCLUSIONS
  Variation in criteria for definitions of index and reference tests, absence of measured glomerular filtration rate in most studies.
  
  
  CONCLUSIONS
  Serum CysC appears to be a good biomarker in the prediction of AKI, whereas urinary CysC excretion has only moderate diagnostic value.
authors: Department of Critical Care Medicine, Jinhua Municipal Central Hospital, Zhejiang, People's Republic of China. zh_zhang1984@hotmail.com
authors: Zhongheng
authors: Z
authors: Zhang
authors: Baolong
authors: B
authors: Lu
authors: Xiaoyan
authors: X
authors: Sheng
authors: Ni
authors: N
authors: Jin