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      Improved equations estimating GFR in children with chronic kidney disease using an immunonephelometric determination of cystatin C

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          Abstract

          The Chronic Kidney Disease in Children study is a cohort of about 600 children with chronic kidney disease (CKD) in the United States and Canada. The independent variable for our observations was a measurement of glomerular filtration rate (GFR) by iohexol disappearance (iGFR) at the first two visits one year apart and during alternate years thereafter. In a previous report, we had developed GFR estimating equations utilizing serum creatinine, blood urea nitrogen, height, gender and cystatin C measured by an immunoturbidimetric method; however the correlation coefficient of cystatin C and GFR (-0.69) was less robust than expected. Therefore, 495 samples were re-assayed using immunonephelometry. The reciprocal of immunonephelometric cystatin C was as well correlated with iGFR as was height/serum creatinine (both 0.88). We developed a new GFR estimating equation using a random 2/3 of 965 person-visits and applied it to the remaining 1/3 as a validation data set. In the validation data set, the correlation of the estimated GFR with iGFR was 0.92 with high precision and no bias; 91% and 45% of eGFR values were within 30% and 10% of iGFR, respectively. This equation works well in children with CKD in a range of GFR from 15 to 75 ml/min per 1.73 m 2. Further studies are needed to establish the applicability to children of normal stature and muscle mass, and higher GFR.

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          Most cited references 39

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          Statistical methods for assessing agreement between two methods of clinical measurement.

          In clinical measurement comparison of a new measurement technique with an established one is often needed to see whether they agree sufficiently for the new to replace the old. Such investigations are often analysed inappropriately, notably by using correlation coefficients. The use of correlation is misleading. An alternative approach, based on graphical techniques and simple calculations, is described, together with the relation between this analysis and the assessment of repeatability.
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            Serum cystatin C is superior to serum creatinine as a marker of kidney function: a meta-analysis.

            Serum cystatin C (Cys C) has been proposed as a simple, accurate, and rapid endogenous marker of glomerular filtration rate (GFR) in research and clinical practice. However, there are conflicting reports regarding the superiority of Cys C over serum creatinine (Cr), with a few studies suggesting no significant difference. We performed a meta-analysis of available data from various studies to compare the accuracy of Cys C and Cr in relation to a reference standard of GFR. A bibliographic search showed 46 articles until December 31, 2001. We also retrieved data from eight other studies presented and published in abstract form. The overall correlation coefficient for the reciprocal of serum Cys C (r = 0.816; 95% confidence interval [CI], 0.804 to 0.826) was superior to that of the reciprocal of serum Cr (r = 0.742; 95% CI, 0.726 to 0.758; P < 0.001). Similarly, receiver operating characteristic (ROC)-plot area under the curve (AUC) values for 1/Cys C had greater identity with the reference test for GFR (mean ROC-plot AUC for Cys C, 0.926; 95% CI, 0.892 to 0.960) than ROC-plot AUC values for 1/Cr (mean ROC-plot AUC for serum Cr, 0.837; 95% CI, 0.796 to 0.878; P < 0.001). Immunonephelometric methods of Cys C assay produced significantly greater correlations than other assay methods (r = 0.846 versus r = 0.784; P < 0.001). In this meta-analysis using currently available data, serum Cys C is clearly superior to serum Cr as a marker of GFR measured by correlation or mean ROC-plot AUC. Copyright 2002 by the National Kidney Foundation, Inc.
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              A simple estimate of glomerular filtration rate in children derived from body length and plasma creatinine.

              Based on statistical analysis of data in 186 children, a formula was derived which allows accurate estimation of glomerular filtration rate (GFR) from plasma creatinine and body lenght (GFR(ml/min/1.73 sq m) = 0.55 length (cm)/Per (mg/dl). Its application to clearance data in a separate group of 223 children reveals excellent agreement with GFR estimated by the Ccr (r = .935) or Cin (r = .905). This formula should be useful for adjusting dosages of drugs excreted by the kidney and detecting significant changes in renal function.
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                Author and article information

                Journal
                0323470
                5428
                Kidney Int
                Kidney Int.
                Kidney international
                0085-2538
                1523-1755
                22 May 2012
                August 2012
                01 February 2013
                : 82
                : 4
                : 445-453
                Affiliations
                [1 ]University of Rochester School of Medicine, Rochester, NY
                [2 ]Johns Hopkins Bloomberg School of Public Health, Baltimore, MD
                [3 ]National Institute of Diabetes and Digestive Kidney Disease, National Institutes of Health, Bethesda, MD
                [4 ]University of Florida College of Medicine and Shands Children’s Hospital, Gainesville, FL
                [5 ]Children’s Mercy Hospital, Kansas City, MO
                [6 ]The Children’s Hospital of Philadelphia, Philadelphia, PA
                Author notes
                Address for correspondence and reprints: George J. Schwartz, M.D., Professor of Pediatrics and of Medicine, Chief, Pediatric Nephrology, Box 777, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester New York 14642, Phone: (585) 275-9784, FAX: (585) 756-8054, George_Schwartz@ 123456urmc.rochester.edu
                Article
                NIHMS371509
                10.1038/ki.2012.169
                3433576
                22622496
                Categories
                Article

                Nephrology

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