***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND AND OBJECTIVES The authors have previously shown that urine neutrophil gelatinase-associated lipocalin ( NGAL ) , measured by a research ELISA , is an early predictive biomarker of acute kidney injury ( AKI ) after cardiopulmonary bypass ( CPB ) . In this study , whether an NGAL immunoassay developed for a st and ardized clinical platform ( ARCHITECT analyzer , Abbott Diagnostics Division , Abbott Laboratories , Abbott Park , IL ) can predict AKI after CPB was tested . DESIGN , SETTING , PARTICIPANTS , & MEASUREMENTS In a pilot study with 136 urine sample s ( NGAL range , 0.3 to 815 ng/ml ) and 6 calibration st and ards ( NGAL range , 0 to 1000 ng/ml ) , NGAL measurements by research ELISA and by the ARCHITECT assay were highly correlated ( r = 0.99 ) . In a subsequent study , 196 children undergoing CPB were prospect ively enrolled and serial urine NGAL measurements obtained by ARCHITECT assay . The primary outcome was AKI , defined as a > or = 50 % increase in serum creatinine . RESULTS AKI developed in 99 patients ( 51 % ) , but the diagnosis using serum creatinine was delayed by 2 to 3 d after CPB . In contrast , mean urine NGAL levels increased 15-fold within 2 h and by 25-fold at 4 and 6 h after CPB . For the 2-h urine NGAL measurement , the area under the curve was 0.95 , sensitivity was 0.82 , and the specificity was 0.90 for prediction of AKI using a cutoff value of 100 ng/ml . The 2-h urine NGAL levels correlated with severity and duration of AKI , length of stay , dialysis requirement , and death . CONCLUSIONS Accurate measurements of urine NGAL are obtained using the ARCHITECT platform . Urine NGAL is an early predictive biomarker of AKI severity after CPB Objective : To compare the value of novel with conventional serum biomarkers in the prediction of  acute kidney injury ( AKI ) in adult cardiac surgical patients according to preoperative renal function . Design : Single-center , prospect i ve observational study . Setting : Tertiary hospital . Patients : One hundred adult cardiac surgical patients . Measurements and Main Results : We measured  concentrations of plasma neutrophil gelatinase-associated lipocalin ( NGAL ) , and serum cystatin C , and creatinine and urea at baseline , on arrival in the intensive care unit ( ICU ) and at 24 hours postoperatively . We assessed such biomarkers in relation to the development of AKI ( > 50 % increase in creatinine from baseline ) and to a composite end point ( need for renal replacement therapy and in-hospital mortality ) . We defined an area under the receiver operating characteristic curve of 0.60–0.69 as poor , 0.70–0.79 as fair , 0.80–0.89 as good , and 0.90–1.00 as excellent in terms of predictive value . On arrival in ICU , plasma NGAL and serum cystatin C were of good predictive value , but creatinine and urea were of poor predictive value . After exclusion of patients with preoperative renal impairment ( estimated glomerular filtration rate < 60 mL/min ) , the predictive performance for AKI of all renal biomarkers on arrival in ICU remained unchanged except for cystatin C , which was of fair value in such patients . At 24 hours postoperatively , all renal biomarkers were of good predictive value . On arrival in ICU , novel biomarkers were superior to conventional biomarkers ( p < 0.05 ) . Plasma NGAL ( p = 0.015 ) and serum cystatin C ( p = 0.007 ) were independent predictors of AKI and of excellent value in the prediction of the composite end point . Conclusions : Early postoperative measurement of plasma NGAL was of good value in identifying patients who developed AKI after adult cardiac surgery .  Plasma NGAL and serum cystatin C were superior to conventional biomarkers in the prediction of AKI and were also of prognostic value in this setting BACKGROUND Acute renal failure ( ARF ) is associated with high mortality . Presently , no specific therapy for ARF exists . Therefore , early detection of ARF is critical to prevent its progression . However , serum creatinine , the st and ard marker to detect ARF , demonstrates major limitations . We prospect ively evaluated whether serum cystatin C detected ARF earlier than serum creatinine . METHODS In 85 patients at high risk to develop ARF , serum creatinine and cystatin C were determined daily . ARF was defined according to the Risk of renal dysfunction , Injury to the kidney , Failure of kidney function , Loss of kidney function  , and ESRD  ( RIFLE ) classification when creatinine increased by > /=50 % ( R- criteria ) , by > /=100 % ( I- criteria ) , or by > /=200 % ( F- criteria ) . In analogy , ARF was detected when cystatin C increased by > /=50 % , by > /=100 % , or by > /=200 % . RESULTS Forty-four patients developed ARF and 41 served as controls . In ARF by R- , I- , and F- criteria , the increase of cystatin C significantly preceded that of creatinine . Specifically , serum cystatin C increased already by > /=50 % 1.5 + /- 0.6 days earlier compared to creatinine . Serum cystatin C demonstrated a high diagnostic value to detect ARF as indicated by area under the curve of the ROC analysis of 0.82 and 0.97 on the two days before the R- criteria was fulfilled by creatinine . Cystatin C detected ARF according to the R- criteria with a sensitivity of 55 % and 82 % on these days , respectively . Cystatin C also performed excellently , detecting ARF defined by the I- and F- criteria two days prior to creatinine , and moderately well predicting renal replacement therapy in the further course of ARF . Additionally , low T(3)- or T(3)/T(4 ) syndrome , glucocorticoid deficiency and excess did not affect cystatin C levels , adding to its usefulness in critically ill patients with ARF . CONCLUSION Serum cystatin C is a useful detection marker of ARF , and may detect ARF one to two days earlier than creatinine We hypothesized that neutrophil gelatinase-associated lipocalin ( NGAL ) is an early predictive biomarker of  contrast-induced nephropathy ( CIN ) . We prospect ively enrolled 91 children ( age 0–18 years ) with congenital heart disease undergoing elective cardiac catheterization and angiography with contrast administration ( CC ; Ioversol ) . Serial urine and plasma sample s were analyzed in a double-blind fashion by NGAL enzyme-linked immunosorbent assay ( ELISA ) . CIN , defined as a 50 % increase in serum creatinine from baseline , was found in 11 subjects ( 12 % ) , but detection using increase in serum creatinine was only possible 6–24 h after CC . In contrast , significant elevation of NGAL concentrations in urine ( 135 ± 32 vs. 11.6 ± 2 ng/ml without CIN , p < 0.001 ) and plasma ( 151 ± 34 vs. 36 ± 4 without CIN , p < 0.001 ) were noted within 2 h after CC in those subjects . Using a cutoff value of 100 ng/ml , sensitivity , specificity , and area under the receiver-operating characteristic ( ROC ) curve for prediction of CIN were excellent for the 2-h urine NGAL ( 73 % , 100 % , and 0.92 , respectively ) and 2-h plasma NGAL ( 73 % , 100 % , and 0.91 , respectively ) . By multivariate analysis , the 2-h NGAL concentrations in the urine ( R2 = 0.52 , p < 0.0001 ) and plasma ( R2 = 0.72 , p < 0.0001 ) were found to be powerful independent predictors of CIN . Patient demographics and contrast volume were not predictive of CIN Introduction Serum creatinine is a late marker of acute kidney injury ( AKI ) . Urine neutrophil gelatinase-associated lipocalin ( uNGAL ) is an early marker of AKI , where the timing of kidney injury is known . It is unknown whether uNGAL predicts AKI in the general critical care setting . We assessed the ability of uNGAL to predict AKI development and severity in critically ill children . Methods This was a prospect i ve cohort study of critically ill children . Children aged between 1 month and 21 years who were mechanically ventilated and had a bladder catheter inserted were eligible . Patients with end-stage renal disease or who had just undergone kidney transplantation were excluded . Patients were enrolled within 24 to 48 hours of initiation of mechanical ventilation .  Clinical data and serum creatinine were collected daily for up to 14 days from enrollment , and urine was collected once daily for up to 4 days for uNGAL measurement . AKI was grade d using pRIFLE ( pediatric modified Risk , Injury , Failure , Loss , End Stage Kidney Disease ) criteria . Day 0 was defined as the day on which the AKI initially occurred , and pRIFLEmax was defined as the worst pRIFLE AKI grade recorded during the study period . The χ2 test was used to compare associations between categorical variables . Mann-Whitney and Kruskal-Wallis tests were used to compare continuous variables between groups . Diagnostic characteristics were evaluated by calculating sensitivity and specificity , and constructing receiver operating characteristic curves . Results A total of 140 patients ( 54 % boys , mean ± st and ard deviation Pediatric Risk of Mortality II score 15.0 ± 8.0 , 23 % sepsis ) were included . Mean and peak uNGAL concentrations increased with worsening pRIFLEmax status ( P < 0.05 ) . uNGAL concentrations rose ( at least sixfold higher than in controls ) in AKI , 2 days before and after a 50 % or greater rise in serum creatinine , without change in control uNGAL . The parameter uNGAL was a good diagnostic marker for AKI development ( area under the receiver operating characteristic curve [ AUC ] 0.78 , 95 % confidence interval [ CI ] 0.62 to 0.95 ) and persistent AKI for 48 hours or longer ( AUC 0.79 , 95 % CI 0.61 to 0.98 ) , but not for AKI severity , when it was recorded after a rise in serum creatinine had occurred ( AUC 0.63 , 95 % CI 0.44 to 0.82 ) . Conclusion We found uNGAL to be a useful early AKI marker that predicted development of severe AKI in a heterogeneous group of patients with unknown timing of kidney injury Introduction Acute kidney injury ( AKI ) is a frequent complication of  cardiopulmonary bypass ( CPB ) . The lack of early biomarkers has impaired our ability to intervene in a timely manner . We previously showed in a small cohort of patients that plasma neutrophil gelatinase-associated lipocalin ( NGAL ) , measured using a research enzyme-linked immunosorbent assay , is an early predictive biomarker of AKI after CPB . In this study we tested whether a point-of-care NGAL device can predict AKI after CPB in a larger cohort . Methods First , in a cross-sectional pilot study including 40 plasma sample s ( NGAL range 60 to 730 ng/ml ) and 12 calibration st and ards ( NGAL range 0 to 1,925 ng/ml ) , NGAL measurements by enzyme-linked immunosorbent assay and by Triage ® NGAL Device ( Biosite Inc. , San Diego , CA , USA ) were highly correlated ( r = 0.94 ) . Second , in a subsequent prospect i ve uncontrolled cohort study , 120 children undergoing CPB were enrolled . Plasma was collected at baseline and at frequent intervals for 24 hours after CPB , and analyzed for NGAL using the Triage ® NGAL device . The primary outcome was AKI , which was defined as a 50 % or greater increase in serum creatinine . Results AKI developed in 45 patients ( 37 % ) , but the diagnosis using serum creatinine was delayed by 2 to 3 days after CPB . In contrast , mean plasma NGAL levels increased threefold within 2 hours of CPB and remained significantly elevated for the duration of the study . By multivariate analysis , plasma NGAL at 2 hours after CPB was the most powerful independent predictor of AKI ( β = 0.004 , P < 0.0001 ) . For the 2-hour plasma NGAL measurement , the area under the curve was 0.96 , sensitivity was 0.84 , and specificity was 0.94 for prediction of AKI using a cut-off value of 150 ng/ml . The 2 hour postoperative plasma NGAL levels strongly correlated with change in creatinine ( r = 0.46 , P < 0.001 ) , duration of AKI ( r = 0.57 , P < 0.001 ) , and length of hospital 
    Output:
    
NGAL level appears to be of diagnostic and prognostic value for AKI