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Published on: May 10, 2013
Comparison of Cystatin C and Creatinine-Based Equations with Measured Glomerular Filtration Rate in a Diverse
Izmarie Poventud-Fuentes1,2, Emily Garnett1,2, Ayse Akcan-Arikan3
1Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA.
Insights
Estimated glomerular filtration rate (eGFR) using cystatin C (CysC)-based equations without race correction accurately approximates measured GFR (mGFR) in diverse pediatric populations. These non-race-corrected CysC equations offer a reliable, less invasive method for assessing kidney function in children.
Area of Science:
- Pediatric Nephrology
- Renal Function Assessment
- Biomarker Analysis
Background:
- Accurate kidney function assessment is crucial for early detection of kidney damage.
- Estimated glomerular filtration rate (eGFR) using serum creatinine and cystatin C (CysC) are standard clinical tools.
- CysC-based equations are preferred in pediatrics due to independence from body composition.
Purpose of the Study:
- To evaluate the performance of various CysC- and creatinine-based eGFR equations against measured GFR (mGFR) in a diverse pediatric cohort.
- To compare race-corrected (RC) and non-race-corrected (NRC) eGFR equations.
- To assess the utility of CysC-based eGFR as a less invasive alternative to mGFR.
Main Methods:
- Retrospective study of 43 pediatric patients (7 months to 21 years) from diverse racial/ethnic backgrounds.
- Comparison of mGFR (using Tc-99mDTPA tracer) with eGFR calculated from 9 different equations.
- Deming regression analysis to assess correlation, bias, and agreement (P30) between mGFR and eGFRs.
Main Results:
- Non-race-corrected (NRC) CysC-based equations showed the best performance.
- Schwartz CysC (NRC) demonstrated the highest accuracy (79.1% within 30% of mGFR) and lowest bias (-14.00 mL/min/1.73 m²).
- Race-corrected equations generally overestimated eGFR, with CKD-EPI CysC-creatinine having the lowest bias among them (34.14 mL/min/1.73 m²).
Conclusions:
- Cystatin C-based eGFR equations, particularly when not race-corrected, provide a reliable approximation of mGFR in pediatric patients.
- These NRC CysC equations serve as a valuable, less invasive method for monitoring kidney function across diverse pediatric populations.
- The findings support the routine use of NRC CysC eGFR equations for pediatric kidney function assessment.
Background:
Accurate assessment of kidney function is essential for early detection of kidney damage. While measured glomerular filtration rate (mGFR) is occasionally used as a reference, estimated GFR (eGFR) from serum creatinine- and cystatin C (CysC)-based equations are routinely used in clinical practice as a reliable and less invasive approach. In pediatric populations, CysC-based equations provide a closer approximation as they are independent of body composition. Limited information is available on the performance of CysC-based equations in comparison with mGFR with tracers other than iohexol. Therefore, the goal of our study was to evaluate how eGFR, based on several CysC- and creatinine-based equations, with and without race correction, relates to mGFR in a diverse pediatric population.
Methods:
A total of 43 patients (7 months to 21 years) from diverse race/ethnicity were retrospectively studied to compare the mGFR from multiple blood sample collections after intravenous tracer injection (Tc-99mDTPA) with eGFR using 9 equations. Deming regression analyses were performed to assess correlation between the mGFR and eGFRs.
Results:
The average mGFR for this cohort was 95.0 mL/min/1.73 m2. Race-corrected (RC) equations gave overestimated eGFR across all ethnic groups, with the lowest bias for Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) CysC-creatinine (34.14 mL/min/1.73 m2). The best correlations to mGFR, percentage of eGFR within 30% of mGFR (P30), and lowest biases were from non-race-corrected (NRC) equations Chronic Kidney Disease in Children (CKiD) (0.6460, 65.1%, 2.86 mL/min/1.73 m2), CKD-EPI CysC (0.6858, 69.8%, 11.01 mL/min/1.73 m2), and Schwartz CysC (0.6876, 79.1%, -14.00 mL/min/1.73 m2).
Conclusion:
Overall, CysC-based equations without race correction provide a good approximation of mGFR and a less invasive alternative to monitoring kidney function in pediatric population, irrespective of race/ethnicity.
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