ESPN 53rd Annual Meeting

ESPN 2021


 
Agreement between creatinine- and cystatine C-based formulas to estimate glomerular filtration rate in Congolese children
Agathe B. Nkoy 1 Therance T. Matoka 1 Dieumerci K. Betukumesu 1 Orly K. Kazadi 1 Ernest K. Sumaili 2 René M. Ngiyulu 1 Pierre Delanaye 3 Etienne Cavalier 4 Lambertus P. Van den Heuvel 5 Elena Levtchenko 5 Pépé M. Ekulu 1

1- Division of Nephrology, Department of Pediatrics, University Hospital of Kinshasa, Faculty of Medicine, University of Kinshasa, Kinshasa, Democratic Republic of Congo.
2- Division of Nephrology, Department of Internal Medicine, University Hospital of Kinshasa, Faculty of Medicine, University of Kinshasa, Kinshasa, Democratic Republic of Congo.
3- Department of Nephrology-Dialysis-Transplantation, CHU Sart Tilman , University of Liège, Liège, Belgium.
4- Division of Clinical Chemistry, CHU Sart Tilman, University of Liège , Liège, Belgium.
5- Department of Development and Regeneration, KU Leuven, Leuven, Belgium.
 
Introduction:

Glomerular filtration rate (GFR) is a critical tool for the diagnosis of kidney diseases. In routine, creatinine-based formula are usually used to estimate GFR (eGFR) in children. However, the accuracy of these formula is highly dependent on the creatinine assay method used. Our study aimed to assess the concordance between the original and the updated Schwartz formula applied to creatinine, regardless of the measurement method used, and the cystatin C formula used as the reference, in healthy children living in the Democratic Republic of Congo (DRC).

Material and methods:

In a cross sectional study conducted from February to December 2019, a random sample of  515 children (aged 6 to 16 years) were recruited using a multistage sampling, from 17 schools in Kinshasa, the capital of the DRC. Using kappa coefficient and Bland-Altman method, we evaluated the agreement between eGFR from the original Schwartz formula applied to Jaffe-based uncalibrated creatinine, from the updated Schwartz formula applied to both Jaffe-based uncalibrated creatinine and enzymatic based-creatinine, and cystatine C-based formula.

Results:

The results showed a strong agreement between eGFR from the original Schwartz formula applied to Jaffe-based uncalibrated creatinine versus cystatine C-based formula (kappa=0.95), and the updated Schwartz formula using enzymatic based-creatinine versus cystatine C-based formula (kappa=0.96).  However, there was a significant gap between eGFR from updated Schwartz formula applied to Jaffe-based uncalibrated creatinine with eGFR from cystatine C-based formula (kappa=0.45).

Conclusions:

The significant difference between the updated Schwartz formula applied to Jaffe-based uncalibrated creatinine and cystatine C-based formula reveals that the new Schwartz formula should be used with caution, especially in low-income countries, like  DRC, where  Jaffe method for determining creatinine remains the most commonly used. In this setting, the use of the original Schwartz formula is more appropriate.