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Published on: May 10, 2013
New standardized cystatin C and creatinine GFR equations in children validated with inulin clearance
Ulla B Berg1, Ulf Nyman, Rune Bäck
1Department of Clinical Science, Intervention and Technology, Division of Pediatrics, Karolinska Institutet, Karolinska University Hospital Huddinge, 14186, Stockholm, Sweden, ulla.berg@ki.se.
Insights
Cystatin C-based equations are preferred for estimating glomerular filtration rate (GFR) in children. Combining cystatin C and creatinine warrants further research for improved accuracy in pediatric GFR assessment.
Area of Science:
- Pediatric Nephrology
- Biomarker Research
- Renal Function Assessment
Background:
- Glomerular filtration rate (GFR) is a key indicator of kidney function in children.
- Accurate GFR estimation is crucial for diagnosing and managing pediatric renal disorders.
- Existing GFR equations rely on markers like creatinine, but their accuracy varies in pediatric populations.
Purpose of the Study:
- To compare the performance of various glomerular filtration rate (GFR) equations in children.
- To evaluate equations based on standardized cystatin C (CYSC) and creatinine (CREA) and their combinations.
- To assess the accuracy of these equations against the gold standard, renal clearance of inulin (C-inulin).
Main Methods:
- A cohort of 220 children with diverse renal conditions underwent C-inulin measurement.
- Performance metrics including bias, precision (IQR), and accuracy (P30) were calculated for multiple GFR equations.
- Equations evaluated included standalone CYSC (CAPACYSC, BergCYSC), CREA (SchwartzCREA, GaoCREA), combined CYSC-CREA (ChehadeCYSC+CREA), and averaged models (MEANCAPA+Schwartz, MEANBERG+SCHWARTZ).
Main Results:
- Cystatin C equations demonstrated favorable performance, with median bias ranging from -7.6% to -4.9% and accuracy (P30) between 86-91%.
- Combined equations showed varied results, with MEANCAPA+Schwartz and MEANBERG+SCHWARTZ achieving high accuracy (89% and 91% P30, respectively).
- Cystatin C-based and combined equations exhibited more stable performance across different pediatric subgroups compared to creatinine-only equations.
Conclusions:
- Standardized cystatin C is a reliable marker for estimating GFR in pediatric populations.
- The combination of cystatin C and creatinine shows potential for improving GFR estimation accuracy in children.
- Further investigation is recommended to fully elucidate the benefits of combining cystatin C and creatinine for pediatric GFR assessment.
Background:
This study compares glomerular filtration rate (GFR) equations in children based on standardized cystatin C (CYSC) and creatinine (CREA) and their combinations with renal clearance of inulin (C-inulin).
Methods:
A total of 220 children with different renal disorders were referred for C-inulin (median 84 ml/min/1.73 m(2)). Bias, precision (interquartile range, IQR), and accuracy (percentage of estimates ±30 % of C-inulin; P30) were evaluated for two cystatin C equations, CAPACYSC and BergCYSC, for creatinine equations, SchwartzCREA and GaoCREA, the arithmetic mean of CAPACYSC and SchwartzCREA (MEANCAPA+Schwartz), BergCYSC and SchwartzCREA (MEANBERG+SCHWARTZ) and the composite equation ChehadeCYSC+CREA.
Results:
Overall results of CAPACYSC, BergCYSC, SchwartzCREA, GaoCREA, MEANCAPA+Schwartz, MEANBERG+SCHWARTZ and ChehadeCYSC+CREA were: median bias -7.6/-4.9/-3.7/-2.3/-4.6/-4.0/-10.1 %, IQR 20.0/19.9/21.7/22.4/21.0/20.9/23.3 ml/min/1.73 m(2) and P30 86/86/80/83/89/91/83 %. The cystatin C equations, MEANCAPA+Schwartz and MEANBERG+SCHWARTZ had a more stable performance across subgroups compared with SchwartzCREA, GaoCREA and ChehadeCYSC+CREA.
Conclusions:
Cystatin C was the preferred filtration marker for GFR estimation in children, while the benefit of combining cystatin C and creatinine deserves further investigations.
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