Chronic kidney disease staging with cystatin C or creatinine-based formulas: flipping the coin

• Published in: Nephrology, dialysis, transplantation Vol. 34; no. 2; pp. 287 - 294
• Main Authors: Luis-Lima, Sergio, Escamilla-Cabrera, Beatriz, Negrín-Mena, Natalia, Estupiñán, Sara, Delgado-Mallén, Patricia, Marrero-Miranda, Domingo, González-Rinne, Ana, Miquel-Rodríguez, Rosa, Cobo-Caso, María Ángeles, Hernández-Guerra, Manuel, Oramas, Juana, Batista, Norberto, Aldea-Perona, Ana, Jorge-Pérez, Pablo, González-Alayón, Carlos, Moreno-Sanfiel, Miguel, González-Rodríguez, Juan Antonio, Henríquez, Laura, Alonso-Pescoso, Raquel, Díaz-Martín, Laura, González-Rinne, Federico, Lavín-Gómez, Bernardo Alio, Galindo-Hernández, Judith, Sánchez-Gallego, Macarena, González-Delgado, Alejandra, Jiménez-Sosa, Alejandro, Torres, Armando, Porrini, Esteban
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01-02-2019
• Subjects: Adult; Aged; Albuminuria - blood; Creatinine - blood; Cystatin C - blood; Disease Progression; Female; Glomerular Filtration Rate; Humans; Male; Middle Aged; Nephrology - standards; Renal Insufficiency, Chronic - blood; Reproducibility of Results; Risk; Severity of Illness Index; measured GFR; cystatin C; creatinine; estimated GFR; CKD staging
• ISSN: 0931-0509; 1460-2385
• DOI: 10.1093/ndt/gfy086

Abstract
Background
Chronic kidney disease (CKD) affects 10–13% of the population worldwide. CKD classification stratifies patients in five stages of risk for progressive renal disease based on estimated glomerular filtration rate (eGFR) by formulas and albuminuria. However, the reliability of formulas to reflect real renal function is a matter of debate. The effect of the error of formulas in the CKD classification is unclear, particularly for cystatin C–based equations.
Methods
We evaluated the reliability of a large number of cystatin C and/or creatinine-based formulas in the definition of the stages of CKD in 882 subjects with different clinical situations over a wide range of glomerular filtration rates (GFRs) (4.2–173.7 mL/min).
Results
Misclassification was a constant for all 61 formulas evaluated and averaged 50% for creatinine-based and 35% for cystatin C–based equations. Most of the cases were misclassified as one stage higher or lower. However, in 10% of the subjects, one stage was skipped and patients were classified two stages above or below their real stage. No clinically relevant improvement was observed with cystatin C–based formulas compared with those based on creatinine.
Conclusions
The error in the classification of CKD stages by formulas was extremely common. Our study questions the reliability of both cystatin C and creatinine-based formulas to correctly classify CKD stages. Thus the correct classification of CKD stages based on estimated GFR is a matter of chance. This is a strong limitation in evaluating the severity of renal disease, the risk for progression and the evolution of renal dysfunction over time.