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New Equation Addresses Kidney Function Across All Age Groups

MedicalResearch.com Interview with:

Prof. Dr. Hans Pottel Professeur Invité (titre honorifique) Faculté de Médecine Université de Liège

Prof. Pottel

Prof. Dr. Hans Pottel PhD
Professeur Invité (titre honorifique)
Faculté de Médecine
Université de Liège
KULeuven-KULAK, Kortrijk, Belgium 

MedicalResearch.com: What is the background for this study? Why do we need a new GFR?

Response: The currently recommended equations have flaws, mainly because there is one equation (CKiD) recommended for children, and one recommended (CKD-EPI) for adults (by KDIGO). When transitioning from pediatric nephrology care to adult nephrology care, the switch from CKiD to CKD-EPI causes implausible jumps (of more than 50%), mainly because CKD-EPI largely overestimates GFR in young adults (18-30 years). The new equation overcomes this problem as it applies for all ages (for children and adults) and overcomes the known flaws of the currently most used equations. The new equation is less biased and more precise across the full age spectrum and for the full range of serum creatinine concentrations.

The equation was developed in 11 251 participants from 7 cohorts (development and internal validation datasets) and validated in 8 378 participants from 6 cohorts (external validation dataset). Data were coming from European and American nephrology centers. No patients of African-American ancestry were included. Actually, the previously published FAS-equation served as the basic mathematical form for the equation, but we adjusted the power coefficients for serum creatinine (very much like it was done in the CKD-EPI equation). You could say that we used properties of both the FAS and CKD-EPI equation to come to an improved equation to estimate GFR.

 MedicalResearch.com: What are the main findings?

Response: The new European Kidney Function Consortium (EKFC) equation is a full age spectrum equation (applicable to children, adults and older adults) with low bias across the full age spectrum and with 6.5% less estimation errors exceeding 30% in children, compared to the CKiD equation, and with 3.1% less estimation errors exceeding 30% in adults, compared to the CKD-EPI equation. Thus, the new EKFC equation shows improved accuracy and precision for estimating GFR from serum creatinine compared to commonly used equations. 

MedicalResearch.com: What should readers take away from your report?

Response: Key in developing this new equation is the ‘rescaling’ of serum creatinine, which is different in children compared to adults, and different in females compared to males, as creatinine is a breakdown product of the muscles. Body shape or muscle mass is partially responsible for differences in creatinine generation. By adjusting creatinine generation before entering it as a variable in the equation, we were able to develop an equation applicable for all ages and without further correction for gender at the GFR-level. All adjustments for differences between populations (children vs adults, males vs females) are made at the creatinine level. We have shown that ‘normalizing’ or ‘rescaling’ serum creatinine with population-specific Q-values (= the median Scr of healthy age/sex matched populations) is key in developing new eGFR-equations. 

MedicalResearch.com: What recommendations do you have for future research as a result of this work?

Response: We are planning to evaluate whether specific Q-values are required for other populations, like African-Americans, Mexican-Americans, Asians, Hispanics, … to fine-tune our new equation for other populations than European populations (which are mainly White or from North-African ancestry).

MedicalResearch.com: Is there anything else you would like to add?

Response: Our equation is valid for Whites only. It requires further research to fine-tune our new equations for other populations. At this moment, it would be wrong to apply our equation to other populations than those for which the equation was designed for.

Citation:

Jonas Björk, Marie Courbebaisse, Lionel Couzi, et al. Development and Validation of a Modified Full Age Spectrum Creatinine-Based Equation to Estimate Glomerular Filtration Rate: A Cross-sectional Analysis of Pooled Data. Annals of Internal Medicine 0;0 [Epub ahead of print 10 November 2020]. doi:https://doi.org/10.7326/M20-4366  

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Last Modified: Nov 12, 2020 @ 5:38 pm

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