Very few biomarkers exist for monitoring chronic kidney disease (CKD). We have recently shown that serum neutrophil gelatinase-associated lipocalin (NGAL) represents a novel biomarker for early identification of acute kidney injury. In this study, we hypothesized that serum NGAL may also represent a biomarker for the quantitation of CKD. Forty-five children with CKD stages 2-4 were prospectively recruited for measurement of serum NGAL, serum cystatin C, glomerular filtration rate (GFR) by Ioversol clearance, and estimated GFR (eGFR) by Schwartz formula. Serum NGAL significantly correlated with cystatin C (r=0.74, P<0.000). Both NGAL and cystatin C significantly correlated with measured GFR (r=0.62, P<0.000; and r=0.71, P<0.000, respectively) as well as with eGFR (r=0.66, P<0.000 and r=0.59, P<0.000, respectively). At GFR levels of >or=30 ml/min per 1.73 m(2), serum NGAL, cystatin C, and eGFR were all significantly correlated with measured GFR. However, in subjects with lower GFRs (<30 ml/min per 1.73 m(2)), serum NGAL levels correlated best with measured GFR (r=0.62), followed by cystatin C (r=0.41). We conclude that (a) both serum NGAL and cystatin C may prove useful in the quantitation of CKD, and (b) by correlation analysis, NGAL outperforms cystatin C and eGFR at lower levels of measured GFR.
Background and objectives: Acute kidney injury (AKI) is a frequent complication of cardiopulmonary bypass (CPB). Serum creatinine (SCr), the current standard, is an inadequate marker for AKI since a delay occurs before SCr rises. Biomarkers that are sensitive and rapidly measurable could allow early intervention and improve patient outcomes. We investigated the value of serum cystatin C as an early biomarker for AKI after pediatric CPB.Design, setting, participants, & measurements: We analyzed data from 374 prospectively enrolled children undergoing CPB. Serum samples were obtained before and at 2, 12, and 24 hours after CPB. Cystatin C was quantified by nephelometry. The primary outcome was AKI, defined as a >50% increase in SCr. Secondary outcomes included severity and duration of AKI, hospital length of stay, and mortality. A multivariable stepwise logistic regression analysis was used to assess predictors of AKI.Results: One hundred nineteen patients (32%) developed AKI using SCr criteria. Serum cystatin C concentrations were significantly increased in AKI patients at 12 hours after CPB (P < 0.0001) and remained elevated at 24 hours (P < 0.0001). Maximal sensitivity and specificity for prediction of AKI occurred at a 12-hour cystatin C cut-off of 1.16 mg/L. The 12-hour cystatin C strongly correlated with severity and duration of AKI as well as length of hospital stay. In multivariable analysis, 12-hour cystatin C remained a powerful independent predictor of AKI.Conclusion: Serum cystatin C is an early predictive biomarker for AKI and its clinical outcomes after pediatric CPB.
Background-Serum creatinine is a delayed marker of acute kidney injury (AKI). Our purpose was to discover and validate novel early urinary biomarkers of AKI after cardiac surgery.
Cystatin C-based GFR formulas can provide an accurate estimation of NucGFR in a pediatric population with a high proportion of transplant recipients and oncology patients.
Previous studies indicate that serum cystatin C predicts incident heart failure in older adults. Children with chronic kidney disease (CKD) develop left ventricular (LV) diastolic dysfunction, often the initial abnormality of cardiac function. We hypothesized that cystatin C might predict LV diastolic dysfunction in children with CKD. Fifty-seven subjects, aged 6-21 years, with stage 2-4 CKD underwent echocardiography. Diastole was assessed from transmitral Doppler [maximum early (E wave) and late (A wave) diastolic flow velocities (E/A ratio)] and from tissue Doppler [septal mitral annular peak velocities (E')]. LV filling pressures were determined, using a ratio of E/E'. Fourteen (25%) patients had low E' and 15 (26%) had high E/E'. Children with abnormal E' or E/E' had significantly higher cystatin C levels than children with normal indices (P<0.05). Neither serum creatinine nor measured glomerular filtration rate (GFR) significantly correlated with E' or E/E'. Stepwise multiple regression analysis showed that cystatin C (beta=-0.825, P=0.023) and left ventricular mass (LVM) index (beta=0.099, P=0.006) independently predicted E'; LVM index independently predicted E/E' (beta=0.0173, P=0.01). We conclude that, in contrast to measured GFR or serum creatinine level, elevated serum cystatin C might be associated with diastolic dysfunction in children with CKD.
Introduction Glomerular filtration rate (GFR) is routinely estimated with cystatin C. In June 2010, the International Federation of Clinical Chemistry (IFCC) released a certified cystatin C reference material (ERM-DA471/IFCC), and new cystatin C glomerular filtration rate estimation (eGFR) equations were developed with the IFCC standard. Early in 2018, Siemens discontinued their nonstandardized cystatin C reagent kits and replaced them with IFCC-calibrated kits in the US market. The aim of the current study was to assess the effect of IFCC calibration on cystatin C values and corresponding GFR estimations. Methods Cystatin C concentration was measured in 81 pediatric patients using a plasma sample from their nuclear GFR measurement with 99mTc-diethylenetriaminepentaaccetic acid. Calibration curves were generated using Siemens nonstandardized and IFCC-standardized kits to measure paired cystatin C concentrations in each sample. GFR-estimating equations using pre-IFCC and IFCC cystatin C values were compared using Bland-Altman analyses. Results The IFCC-standardized assay resulted in a mean increase in the measured cystatin C value of 24%. Estimating equations consistently overestimated GFR prior to IFCC standardization. Following incorporation of the IFCC standard, the Full Age Spectrum equation demonstrated the best overall performance, whereas the Chronic Kidney Disease in Children (CKiD) equation was more accurate in children with decreased GFR. Conclusion Incorporation of the IFCC standard significantly increased cystatin C values and affected the performance of GFR estimating equations. Clinical laboratories and providers may need to update the equation used for cystatin C–based estimation of GFR following adoption of the IFCC reference standard.
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