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• W2789065452 abstract "The bedside Schwartz equation has long been and still is the recommended equation to estimate glomerular filtration rate (GFR) in children. However, this equation is probably best suited to estimate GFR in children with chronic kidney disease (reduced GFR) but is not optimal for children with GFR >75 mL/min/1.73 m2. Moreover, the Schwartz equation requires the height of the child, information that is usually not available in the clinical laboratory. This makes automatic reporting of estimated glomerular filtration rate (eGFR) along with serum creatinine impossible. As the majority of children (even children referred to nephrology clinics) have GFR >75 mL/min/1.73 m2, it might be interesting to evaluate possible alternatives to the bedside Schwartz equation. The pediatric form of the Full Age Spectrum (FAS) equation offers an alternative to Schwartz, allowing automatic reporting of eGFR since height is not necessary. However, when height is involved in the FAS equation, the equation is essentially equal to the Schwartz equation for children, but there are large differences for adolescents. Combining standardized biomarkers increases the prediction performance of eGFR equations for children, reaching P10 ≈ 45% and P30 ≈ 90%. There are currently good and simple alternatives to the bedside Schwartz equation, but the more complex equations combining serum creatinine, serum cystatin C, and height show the highest accuracy and precision. The bedside Schwartz equation has long been and still is the recommended equation to estimate glomerular filtration rate (GFR) in children. However, this equation is probably best suited to estimate GFR in children with chronic kidney disease (reduced GFR) but is not optimal for children with GFR >75 mL/min/1.73 m2. Moreover, the Schwartz equation requires the height of the child, information that is usually not available in the clinical laboratory. This makes automatic reporting of estimated glomerular filtration rate (eGFR) along with serum creatinine impossible. As the majority of children (even children referred to nephrology clinics) have GFR >75 mL/min/1.73 m2, it might be interesting to evaluate possible alternatives to the bedside Schwartz equation. The pediatric form of the Full Age Spectrum (FAS) equation offers an alternative to Schwartz, allowing automatic reporting of eGFR since height is not necessary. However, when height is involved in the FAS equation, the equation is essentially equal to the Schwartz equation for children, but there are large differences for adolescents. Combining standardized biomarkers increases the prediction performance of eGFR equations for children, reaching P10 ≈ 45% and P30 ≈ 90%. There are currently good and simple alternatives to the bedside Schwartz equation, but the more complex equations combining serum creatinine, serum cystatin C, and height show the highest accuracy and precision. Clinical Summary•The pediatric form of the Full Age Spectrum (FAS) equation offers an alternative to the bedside Schwartz equation, allowing automatic reporting of estimated glomerular filtration rate (eGFR) since height is not necessary, and mostly not available in the clinical laboratory.•Combining standardized biomarkers increases the prediction performance of eGFR equations for children, reaching P10 ≈ 45% and P30 ≈ 90%. The bivariate Schwartz equation and the multiplicative form of the FAS equation are very similar.•eGFR equations perform best in the population for whom they were originally designed for, with preference for FAS in healthy and mildly kidney diseased children (GFR > 60 mL/min/1.73 m2) and with preference for Schwartz in the kidney diseased children (GFR < 60 mL/min/1.73 m2).•We recommend that clinical laboratories should report serum creatinine along with the height-independent FAS prediction. Clinicians would use the height-dependent FAS, and in case, the FAS eGFR is < 60 mL/min/1.73 m2, use the Schwartz equation to obtain a second estimate of GFR. •The pediatric form of the Full Age Spectrum (FAS) equation offers an alternative to the bedside Schwartz equation, allowing automatic reporting of estimated glomerular filtration rate (eGFR) since height is not necessary, and mostly not available in the clinical laboratory.•Combining standardized biomarkers increases the prediction performance of eGFR equations for children, reaching P10 ≈ 45% and P30 ≈ 90%. The bivariate Schwartz equation and the multiplicative form of the FAS equation are very similar.•eGFR equations perform best in the population for whom they were originally designed for, with preference for FAS in healthy and mildly kidney diseased children (GFR > 60 mL/min/1.73 m2) and with preference for Schwartz in the kidney diseased children (GFR < 60 mL/min/1.73 m2).•We recommend that clinical laboratories should report serum creatinine along with the height-independent FAS prediction. Clinicians would use the height-dependent FAS, and in case, the FAS eGFR is < 60 mL/min/1.73 m2, use the Schwartz equation to obtain a second estimate of GFR. Estimating glomerular filtration rate (GFR) in children has a 40-year-old history, dating back to 1976 when Schwartz and colleagues1Schwartz G.J. Haycock G.B. Edelmann C.M. Spitzer M. A simple estimate of glomerular filtration rate in children derived from body length and plasma creatinine.Pediatrics. 1976; 58: 259-263Crossref PubMed Google Scholar published his very simple bedside formula eGFR = 0.55 × L/Scr, where L is the height of the child and Scr represents serum creatinine (Scr) expressed in mg/dL. The coefficient of 0.55 has been replaced by 0.413 for children and adolescents, when isotope dilution mass spectroscopy (IDMS) standardized assays for Scr became available.2Schwartz G.J. Muñoz A. Schneider M.F. Mak R.H. Kaskel F. Warady B.A.F.S. New equations to estimate GFR in children with CKD.J Am Soc Nephrol. 2009; 20: 629-637Crossref PubMed Scopus (2410) Google Scholar The height of the child serves as surrogate for muscle mass, since creatinine, which is a breakdown product of muscle mass, changes during growth of the child. The Schwartz formula has been recommended by KDIGO to estimate GFR in children. One downside of this equation is the need for the height of the child, which is commonly not available in the clinical laboratory, making automatic reporting of estimated glomerular filtration rate (eGFR) along with Scr impossible. Automatic reporting of eGFR for adults is mandatory in many countries, allowing early identification of patients with chronic kidney disease (CKD), with evidence demonstrating the benefits of early referrals.3Lunn A. Automatic reporting of creatinine-based estimated glomerular filtration rate in children: is this feasible?.EMJ Nephrol. 2016; 4: 106-112Google Scholar Indeed, in adults, evidence-based strategies have been shown to prevent progression of CKD.4Black C. Sharma P. Scotland G. et al.Early referral strategies for management of people with markers of renal disease: a systematic review of the evidence of clinical effectiveness, cost-effectiveness and economic analysis.Health Technol Assess. 2010; 14: 1-184Crossref PubMed Scopus (152) Google Scholar The rationale for automatic reporting in children is less clear, since there are multiple risk factors, such as hypertension and proteinuria, for progression of CKD in children. Moreover, the incidence of CKD in children is much lower than in the adult population. However, early reporting of decreased eGFR may allow early detection and intervention which can only be to the benefit of the child. In a recent overview, Pottel5Pottel H. Measuring and estimating glomerular filtration rate in children.Pediatr Nephrol. 2017; 32: 249-263Crossref PubMed Scopus (58) Google Scholar has extensively reported on the different eGFR equations for children, and therefore, in this review, we will focus on alternative equations applicable to (multiple) biomarkers for standardized assays only. We then give specific insights comparing the bedside Schwartz equation with the pediatric part of the Full Age Spectrum (FAS) equation. Next, we elaborate on the possibility to define kidney function based on the reference interval of single biomarkers or the combination of biomarkers, without using eGFR equations. Finally, we present the prediction performance of eGFR equations combining multiple (standardized) biomarkers, namely Scr and serum cystatin C (ScysC), using real measured GFR data as comparison. The gold standard method to obtain measured GFR (mGFR) is kidney clearance of inulin, but several reference methods have shown acceptable accuracy with sufficient scientific evidence.6Soveri I. Berg U.B. Björk J. et al.Measuring GFR: a systematic review.Am J Kidney Dis. 2014; 64: 411-424Abstract Full Text Full Text PDF PubMed Scopus (308) Google Scholar The mGFR data used in this article have been obtained by the gold standard inulin kidney clearance method or by iohexol or 51Cr-EDTA plasma clearance, using the slope-intercept method followed by the Bröchner-Mortensen correction.7Bröchner-Mortensen J. A Simple method for the determination of glomerular filtration rate.Scand J Clin Lab Investig. 1972; 30: 271-274Crossref PubMed Scopus (807) Google Scholar Standardization of Scr assays with reference to the gold standard IDMS method has been introduced some 10–15 years ago. Most enzymatic Scr assays are nowadays equivalent to the IDMS method. The data used in this article were all obtained with IDMS traceable enzymatic Scr assays, and it should be emphasized that this is critically important for children that have lower Scr values, requiring high accuracy and precision results.8Delanghe J.R. How to estimate GFR in children.Nephrol Dial Transpl. 2009; 24: 714-716Crossref PubMed Scopus (35) Google Scholar Indeed, compensated Jaffe assays may give negative Scr concentrations after compensation (= subtracting a constant value) in very young children. Limits of quantitation of the assays should be as low as 0.15 mg/dL, since newborns typically have Scr values of about 0.23 mg/dL 1 month after birth.9Pottel H. Vrydags N. Mahieu B. Vandewynckele E. Croes K. Martens F. Establishing age/sex related serum creatinine reference intervals from hospital laboratory data based on different statistical methods.Clin Chim Acta. 2008; 396: 49-55Crossref PubMed Scopus (129) Google Scholar Many clinical laboratories still use the Jaffe-type Scr assays instead of enzymatic Scr assays due to the higher cost of the latter, but the gap becomes smaller and more and more laboratories switch to enzymatic assays, especially for children. The situation is different for ScysC. In 2010, there became a certified standard available (ERM-DA471/IFCC)10Grubb A. Blirup-Jensen S. Lindström V. et al.First certified reference material for cystatin C in human serum ERM-DA471/IFCC.Clin Chem Lab Med. 2010; 48: 1619-1621Crossref PubMed Google Scholar against which ScysC-assays could be calibrated, and only very recently a candidate isotope dilution mass spectrometry method for cystatin C was presented and can potentially serve as gold standard method.11Bargnoux A.S. Piéroni L. Cristol J.P. et al.Société Française de Biologie Clinique (SFBC)Multicenter Evaluation of Cystatin C Measurement after Assay Standardization.Clin Chem. 2017; 63: 833-841Crossref PubMed Scopus (41) Google Scholar Part of the data in this study were obtained with the calibrated particle enhanced turbidimetric (PETIA, Tina quant®) assay of Roche, and part of the data were obtained with the calibrated particle enhanced nephelometric (PENIA) method of Siemens. Calibration of cystatin C assays is as essential as for Scr. Although there is still work to do, as the current certified material is about five times higher than the “normal” cystatin C values, and only a one-point calibration is applied, it has been shown that calibration against the certified material reduces variability and increases accuracy.11Bargnoux A.S. Piéroni L. Cristol J.P. et al.Société Française de Biologie Clinique (SFBC)Multicenter Evaluation of Cystatin C Measurement after Assay Standardization.Clin Chem. 2017; 63: 833-841Crossref PubMed Scopus (41) Google Scholar, 12Ebert N. Delanaye P. Shlipak M. et al.Cystatin C standardization decreases assay variation and improves assessment of glomerular filtration rate.Clin Chim Acta. 2016; 456: 115-121Crossref PubMed Scopus (28) Google Scholar To our knowledge, there are only a very limited number of combined Scr and ScysC-based eGFR equations for children available that were obtained with reference to IDMS traceable Scr and the certified standard for ScysC. Although the best performing combined Schwartz equation was based on height, Scr, ScysC, blood urea nitrogen, and gender, ScysC was not calibrated against the certified standard when this equation was derived. This complex Schwartz formula was originally published in 2009 using turbidimetric ScysC values13Schwartz G.J. Munoz A. Schneider M.F. et al.New equations to estimate GFR in children with CKD.J Am Soc Nephrol. 2009; 20: 629-637Crossref PubMed Scopus (1051) Google Scholar and waseGFR=39.1(Ht/Scr)0.516(1.8/CysC)0.294(30/BUN)0.1691.099male(Ht/1.4)0.188 The equation was reevaluated using immunonephelometric ScysC values14Schwartz G.J. Schneider M.F. Maier P.S. et al.Improved equations estimating GFR in children with chronic kidney disease using an immunonephelometric determination of cystatin C.Kidney Int. 2012; 82: 445-453Abstract Full Text Full Text PDF PubMed Scopus (339) Google Scholar and waseGFR=39.8(Ht/Scr)0.456(1.8/CysC)0.418(30/BUN)0.0791.076male(Ht/1.4)0.179 This Chronic Kidney Disease in Children Cohort Study equation showed high accuracy and precision and minimal bias in the Chronic Kidney Disease in Children Cohort Study population, that is, this equation worked well in children with CKD in a range of GFR from 15 to 75 mL/min/1.73 m2. Confirmation of the utility of this equation is desirable in other populations of children (healthy and diseased), but both equations suffer from the drawback that ScysC has not been calibrated against the certified standard, and since its original publication in 2009 and republication in 2012, only a limited number of external validation studies for both equations have been published.15Chehade H. Cachat F. Jannot A.S. et al.Combined serum creatinine and cystatin C schwartz formula predicts kidney function better than the combined CKD-EPI formula in children.Am J Nephrol. 2013; 38: 300-306Crossref PubMed Scopus (11) Google Scholar, 16Chehade H. Cachat F. Jannot A.S. et al.New combined serum creatinine and cystatin C Quadratic formula for GFR assessment in children.Clin J Am Soc Nephrol. 2014; 9: 54-63Crossref PubMed Scopus (28) Google Scholar, 17Deng F. Finer G. Haymond S. Brooks E. Langman C.B. Applicability of estimating glomerular filtration rate equations in pediatric patients: comparison with a measured glomerular filtration rate by iohexol clearance.Translational Res. 2015; 165: 437-445Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar, 18Siddique K. Leonard D. Borders L. Seikaly M.G. Validation of the CKiD formulae to estimate GFR in children post renal transplant.Pediatr Nephrol. 2014; 29: 445-451Crossref PubMed Scopus (10) Google Scholar, 19Westland R. Abraham Y. Bökenkamp A. Stoffel-Wagner B. Schreuder M.F. van Wijk J.A.E. Precision of estimating equations for GFR inChildren with a Solitary functioning kidney: the KIMONO study.Clin J Am Soc Nephrol. 2013; 8: 764-772Crossref PubMed Scopus (32) Google Scholar, 20Zachwiejaa K. Korohodab P. Kwinta-Rybickac J. et al.Modification of the Schwartz equations for children increases their accuracy at eGFR > 60 mL/min/1.73 m2.Ren Fail. 2016; 38: 787-798Crossref PubMed Scopus (3) Google Scholar, 21Leiona F. Hegbranta J. den Bakker E. et al.Estimating glomerular filtration rate (GFR) in children. The average between a cystatin C- and a creatinine-based equation improves estimation of GFR in both children and adults and enables diagnosing Shrunken Pore Syndrome.Scand J Clin Lab Invest. 2017; 77: 338-344Crossref PubMed Scopus (30) Google Scholar We have used the univariate (for Scr or ScysC) and bivariate form (with both Scr and ScysC) of the above equation (without the blood urea nitrogen information) on our data to compare it with alternative equations. An overview of the equations used in this study is given in Table 1.Table 1Overview of Equations Used in This Comparison Study, With Reference to the Original PublicationName (Reference)EquationSchwartzbed2Schwartz G.J. Muñoz A. Schneider M.F. Mak R.H. Kaskel F. Warady B.A.F.S. New equations to estimate GFR in children with CKD.J Am Soc Nephrol. 2009; 20: 629-637Crossref PubMed Scopus (2410) Google Scholar0.413 Ht/Scr (Scr in mg/dL, Ht in cm)Schwartzcrea14Schwartz G.J. Schneider M.F. Maier P.S. et al.Improved equations estimating GFR in children with chronic kidney disease using an immunonephelometric determination of cystatin C.Kidney Int. 2012; 82: 445-453Abstract Full Text Full Text PDF PubMed Scopus (339) Google Scholar42.3 (Ht/Scr)0.780 (Scr in mg/dL, Ht in m)SchwartzcysC14Schwartz G.J. Schneider M.F. Maier P.S. et al.Improved equations estimating GFR in children with chronic kidney disease using an immunonephelometric determination of cystatin C.Kidney Int. 2012; 82: 445-453Abstract Full Text Full Text PDF PubMed Scopus (339) Google Scholar40.9 (1.8/ScysC)0.931 (ScysC in mg/L)Schwartzcombi14Schwartz G.J. Schneider M.F. Maier P.S. et al.Improved equations estimating GFR in children with chronic kidney disease using an immunonephelometric determination of cystatin C.Kidney Int. 2012; 82: 445-453Abstract Full Text Full Text PDF PubMed Scopus (339) Google Scholar41.6 (Ht/Scr)0.443 (1.8/CysC)0.479 (Scr in mg/dL, ScysC in mg/L, Ht in m)FAScrea26Pottel H. Mottaghy F.M. Zaman Z. Martens F. On the relationship between glomerular filtration rate and serum creatinine in children.Pediatr Nephrol. 2010; 25: 927-934Crossref PubMed Scopus (86) Google Scholar, 27Pottel H. Hoste L. Martens F. A simple height-independent equation for estimating glomerular filtration rate in children.Pediatr Nephrol. 2012; 27: 973-979Crossref PubMed Scopus (91) Google Scholar, 28Hoste L. Dubourg L. Selistre L. et al.A new equation to estimate the glomerular filtration rate in children, adolescents and young adults.Nephrol Dial Transpl. 2013; 29: 944-947Google Scholar107.3/[Scr/Qcrea] with Qcrea (mg/dL) function of age (Table 2) or usingQcrea(Age) = 0.21 + 0.057 × Age − 0.0075 × Age2 + 0.00064 × Age³ − 0.000016 × Age4 for boysQcrea(Age) = 0.23 + 0.034 × Age − 0.0018 × Age2 + 0.00017 × Age³ − 0.0000051 × Age4 for girlsFAScrea(Ht)28Hoste L. Dubourg L. Selistre L. et al.A new equation to estimate the glomerular filtration rate in children, adolescents and young adults.Nephrol Dial Transpl. 2013; 29: 944-947Google Scholar107.3/[Scr/Qcrea] with Qcrea (mg/dL) function of height (Table 2) or usingQcrea(height) = 3.94 − 13.4 × Ht + 17.6 × Ht2 − 9.84 × Ht³ + 2.04 × Ht4 (Ht in m)FAScysC23Pottel H. Delanaye P. Schaeffner E. et al.Estimating glomerular filtration rate for the full age spectrum from serum creatinine and cystatin C.Nephrol Dial Transpl. 2017; 32: 497-507PubMed Google Scholar107.3/[ScysC/QcysC] with QcysC = 0.82 mg/L for childrenFAScombi and FAScombi(Ht)23Pottel H. Delanaye P. Schaeffner E. et al.Estimating glomerular filtration rate for the full age spectrum from serum creatinine and cystatin C.Nephrol Dial Transpl. 2017; 32: 497-507PubMed Google Scholar107.3/[Scr/Qcrea + ScysC/QcysC]FASMult and FASMult(Ht) (unpublished)107.3/ScrQcreaxScysCQcysCLM-REV29Nyman U. Björk J. Lindström V. Grubb A. The Lund-Malmö creatinine-based glomerular filtration rate prediction equation for adults also performs well in children.Scand J Clin Lab Invest. 2008; 68: 568-576Crossref PubMed Scopus (35) Google ScholarLM-REV = exp[X – 0.0158 × Age + 0.438 × ln(Age)] withX = 2.50 + 0.0121 × (150 − Scr), for females and Scr <150 μmol/LX = 2.50 − 0.926 × ln(Scr/150), for females and Scr ≥150 μmol/L:X = 2.56 + 0.00968 × (180 − Scr), for males and Scr<180 μmol/L:X = 2.56 − 0.926 × ln(Scr/180), for males, and Scr ≥180 μmol/LConversion: Scr (mg/dL) = Scr(μmol/L)/88.4CAPA30Grubb A. Horio M. Hansson L.-O. et al.Generation of a new cystatin C-Based estimating equation for glomerular filtration rate by Use of 7 assays standardized to the International calibrator.Clin Chem. 2014; 60: 974-986Crossref PubMed Scopus (201) Google Scholar130 × ScysC−1.069 × age−0.117 − 7 (ScysC in mg/L)Abbreviations: CAPA, Caucasian Asian Pediatric Adult; FAS, Full Age Spectrum; LM-REV, revised Lund-Malmö; Scr, serum creatinine. Open table in a new tab Abbreviations: CAPA, Caucasian Asian Pediatric Adult; FAS, Full Age Spectrum; LM-REV, revised Lund-Malmö; Scr, serum creatinine. In the following section, we restrict ourselves to equations that were derived and are applicable to standardized biomarkers Scr and ScysC. Recently, Pottel and colleagues22Pottel H. Hoste L. Dubourg L. et al.An estimated glomerular filtration rate equation for the full age spectrum.Nephrol Dial Transpl. 2016; 31: 798-806Crossref PubMed Scopus (270) Google Scholar, 23Pottel H. Delanaye P. Schaeffner E. et al.Estimating glomerular filtration rate for the full age spectrum from serum creatinine and cystatin C.Nephrol Dial Transpl. 2017; 32: 497-507PubMed Google Scholar published the FAS equation to estimate GFR from Scr and/or ScysC, or from the combination of both biomarkers. The pediatric form (which is actually valid between 2 and 40 years of age) of the Scr-based FAS equation is a very simple equation:FAScrea=107.3/[Scr/Qcrea] The form of this equation follows from modeling the data of Piepsz24Piepsz A. Tondeur M. Ham H.R. Revisiting normal (51)Cr-ethylenediaminetetraacetic acid clearance values in children.Eur J Nucl Med Mol Imaging. 2006; 33: 1477-1482Crossref PubMed Scopus (117) Google Scholar, 25Piepsz A. Tondeur M. Ham H. Escaping the correction for body surface area when calculating glomerular filtration rate in children.Eur J Nucl Med Mol Imaging. 2008; 35: 1669-1672Crossref PubMed Scopus (31) Google Scholar and establishing a plateau value of 107.3 mL/min/1.73 m2 for healthy children between 2 and 15 years of age. As Scr raises linearly with age in that age period and following the correlation between GFR and the reciprocal of creatinine, Pottel and colleagues26Pottel H. Mottaghy F.M. Zaman Z. Martens F. On the relationship between glomerular filtration rate and serum creatinine in children.Pediatr Nephrol. 2010; 25: 927-934Crossref PubMed Scopus (86) Google Scholar normalized Scr to make it independent of age (and sex) and established a direct relationship between the value of 107.3 mL/min/1.73 m2 and the reciprocal of this normalized Scr. When a child has a Scr level equal to the Qcrea value, which is defined as the mean or median Scr value of the 1-year age-specific distribution of Scr of healthy children, then Scr/Qcrea = 1 and eGFR = 107.3 mL/min/1.73 m2, the mean GFR value for healthy children. The concept of the FAS equation is that it essentially matches mean Scr levels with mean GFR levels in healthy populations. The pediatric FAS equation was first published in 201227Pottel H. Hoste L. Martens F. A simple height-independent equation for estimating glomerular filtration rate in children.Pediatr Nephrol. 2012; 27: 973-979Crossref PubMed Scopus (91) Google Scholar and extended by Hoste and colleagues28Hoste L. Dubourg L. Selistre L. et al.A new equation to estimate the glomerular filtration rate in children, adolescents and young adults.Nephrol Dial Transpl. 2013; 29: 944-947Google Scholar to adolescents in 2015 and is now extended to the full age spectrum.22Pottel H. Hoste L. Dubourg L. et al.An estimated glomerular filtration rate equation for the full age spectrum.Nephrol Dial Transpl. 2016; 31: 798-806Crossref PubMed Scopus (270) Google Scholar It has been shown that this concept also applies for other biomarkers: Scr/Qcrea can be replaced by ScysC/QcysC or a combination of both biomarkers, for example, the average of both normalized biomarkers: (Scr/Qcrea + ScysC/QcysC)/2. In case of ScysC, the normalization factor QcysC = 0.82 mg/L23 (Table 1). Other eGFR equations have been developed for children, but none of them combines standardized Scr and ScysC in one equation for children. However, it has recently been shown that combining the Scr-based revised Lund-Malmö (LM-REV) equation29Nyman U. Björk J. Lindström V. Grubb A. The Lund-Malmö creatinine-based glomerular filtration rate prediction equation for adults also performs well in children.Scand J Clin Lab Invest. 2008; 68: 568-576Crossref PubMed Scopus (35) Google Scholar with the ScysC-based CAPA equation30Grubb A. Horio M. Hansson L.-O. et al.Generation of a new cystatin C-Based estimating equation for glomerular filtration rate by Use of 7 assays standardized to the International calibrator.Clin Chem. 2014; 60: 974-986Crossref PubMed Scopus (201) Google Scholar also shows higher accuracy and precision than any single biomarker–based equation.31Björk J. Grubb A. Larsson A. et al.Accuracy of GFR estimating equations combining standardized cystatin C and creatinine assays: a cross-sectional study in Sweden.Clin Chem Lab Med. 2015; 53: 403-414Crossref PubMed Scopus (68) Google Scholar The LM-REV equation and CAPA equation are also presented in Table 1. Combining LM-REV with CAPA simply means to take the mean of both equations: (LM-REV + CAPA)/2. Contrary to the FAS equation, which is based on the concept that mean normalized Scr matches mean GFR, the LM-REV and CAPA equations, like all other eGFR equations, have been derived from statistical modeling of measured GFR data against Scr (or ScysC) and demographic variables. In the following sections, we focus on the popular bedside Schwartz equation and compare it to the pediatric FAS equation, find out the benefits of using combined biomarkers as such and combined biomarker equations, by comparing the combined Schwartz equation, the combined FAS equation, and the combination of Lund-Malmö and CAPA to measured GFR. The normalization factor Qcrea in the pediatric FAS equation can be obtained in two different ways: (1) Qcrea can be considered as the mean Scr value of the age-specific distribution of healthy children, but (2) Qcrea can also be matched to the height of the child, by use of growth curves (Table 2). Table 2 should be interpreted with caution, as these values have been determined in a Belgian population of healthy children. The mean Scr values were obtained from a large hospital database9Pottel H. Vrydags N. Mahieu B. Vandewynckele E. Croes K. Martens F. Establishing age/sex related serum creatinine reference intervals from hospital laboratory data based on different statistical methods.Clin Chim Acta. 2008; 396: 49-55Crossref PubMed Scopus (129) Google Scholar which was subdivided according to age/gender. For each 1-year age period, the Scr values of healthy children were selected and the mean/median (which is the same when the distribution is Gaussian) is presented as Qcrea in Table 2. National Belgian growth curves32Roelants M. Hauspie R. Hoppenbrouwers K. References for growth and pubertal development from birth to 21 years in Flanders.Belgium Ann Hum Biol. 2009; 36: 680-694Crossref PubMed Scopus (260) Google Scholar were used to match age with mean height of the children. To estimate GFR from Scr, there are two possibilities: either the Qcrea corresponding to the age of the child can be considered or the Qcrea corresponding to the height of the child can be chosen, which are not necessarily the same for a child at a specific age with a specific height. This is especially true during adolescence, where children may be variable in height at the same age. Height is probably a better indicator for muscle mass and thus for the corresponding Scr value. This is also the reason why the FAS equation with Qcrea(height) gives better predictions than the FAS equation with Qcrea(Age).22Pottel H. Hoste L. Dubourg L. et al.An estimated glomerular filtration rate equation for the full age spectrum.Nephrol Dial Transpl. 2016; 31: 798-806Crossref PubMed Scopus (270) Google Scholar, 33Schwartz G.J. Height: the missing link in estimating glomerular filtration rate in children and adolescents.Nephrol Dial Transpl. 2014; 29: 944-947Crossref PubMed Scopus (14) Google ScholarTable 2Mean or Median Scr Values for Healthy Children (Qcrea) in mg/dL, According to Age or Height (Ht)Ht (cm)Qcrea (mg/dL)Age (y) 175.00.26 287.00.29 395.50.31 4102.50.34 5110.00.38 6116.70.41 7123.50.44 8129.50.46 9135.00.49 10140.00.51 11146.00.53 12152.50.57 13159.00.59 14165.00.61Males 15172.00.72 16176.00.78 17178.00.82 18179.00.85 19180.00.88 20181.50.90Females 15164.50.64 16166.00.67 17166.50.69 18167.00.69 19167.50.70 20168.00.70Abbreviation: Scr, serum creatinine. Open table in a new tab Abbreviation: Scr, serum creatinine. Hoste and colleagues28Hoste L. Dubourg L. Selistre L. et al.A new equation to estimate the glomerular filtration rate in children, adolescents and young adults.Nephrol Dial Transpl. 2013; 29: 944-947Google Scholar have modeled the Qcrea values against age, and Qcrea against height, to allow interpolation (to predict Qcrea for values in between the values in Table 2), resulting in 4th degree polynomials (Table 1). Note that there are two polynomials for Qcrea(Age) due to the difference between adolescent males and females, that is, adolescent males gain muscle mass in a much faster way than females in this age period, starting from Qcrea = 0.61 mg/dL at 14 years of age, on average, and reaching the average plateau value of 0.90 mg/dL, whereas females only reach the value of 0.70 mg/dL. Qcrea(height) could be modeled in one 4th degree po" @default.
• W2789065452 created "2018-03-06" @default.
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• W2789065452 date "2018-01-01" @default.
• W2789065452 modified "2023-10-18" @default.
• W2789065452 title "Alternatives for the Bedside Schwartz Equation to Estimate Glomerular Filtration Rate in Children" @default.
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