A Comparison of GFR Estimation Formulae in Pediatric Oncology

Abstract

Background Application of potentially nephrotoxic chemotherapy requires continuous monitoring of renal function for toxicity and dosing. Novel pediatric glomerular filtration rate (GFR) estimating equations including cystatin C have been proposed to enhance the reliability of GFR calculation.

Materials and methods We examined a pediatric oncologic data set with a total of 363 GFR measurements. An analysis of distribution characteristics and comparison of medians was performed to compare creatinine and cystatin C-based GFR estimating formulae. Furthermore, we investigated the clinical impact of different equations in regard to therapeutic consequences.

Results Significant differences in estimated GFR values were calculated depending on the applied formula (range of median GFR from 94.8 to 180.9 mL/min per 1.73 m²) which may result in different therapeutic consequences for the use of potentially nephrotoxic chemotherapeutic agents. Significant correlation for all examined formulae was identified, however there were large fluctuations among the correlation coefficients ranging from 0.254 to 1.0.

Conclusion This study compares proposed pediatric GFR estimating equations in a clinical setting. It underlines the current limitations and difficulties of GFR estimation including potential dosing errors. Cystitis C-based equations can be used as alternatives to creatinine-based estimations when the appropriate laboratory method has been applied. A comparative calculator for pediatric GFR estimating equations along with background information is provided at http://gfr.pedz.de and may support clinical decision-making.

Zusammenfassung

Hintergrund Das Verabreichen von chemotherapeutischen Substanzen mit potentieller Nephrotoxizität setzt ein kontinuierliches Monitoring der renalen Funktion für mögliche Dosisanpassungen voraus. Zur Erhöhung der Reliabilität einer Schätzung der glomerulären Filtrationsrate (GFR) werden in der Pädiatrie zunehmend Cystatin C basierte Formeln vorgeschlagen.

Material und Methoden Wir untersuchten ein pädiatrisch onkologisches Kollektiv mit insgesamt 363 GFR Messungen. Eine deskriptiv statistische Analyse mit Verteilungsverhalten der Mediane wurde durchgeführt um Kreatinin und Cystatin C-basierte GFR Schätzformeln zu vergleichen. Zudem wurden die klinischen Implikationen der unterschiedlichen Formeln im Hinblick auf therapeutische Konsequenzen untersucht.

Ergebnisse Es zeigten sich signifikante Unterschiede der geschätzten GFR Werte in Abhängigkeit der benutzen Formel (Spannweite Median 94.8 bis 180.9 mL/min pro 1.73 m²) die zu unterschiedlichen therapeutischen Konsequenzen für die Nutzung potentiell nephrotoxischer Substanzen führen können. Es ergab sich eine signifikante Korrelation zwischen allen untersuchten Formeln, allerdings zeigte sich eine große Fluktuation des Korrelationskoeffizienten von 0.254 bis 1.0.

Schlussfolgerung Diese Studie vergleicht vorgeschlagene GFR Formeln in einem klinischen Setting. Sie zeigt die derzeitigen Limitationen und Probleme einer GFR Schätzung inklusive potentieller Dosierungsfehler auf. Cystatin C basierte Formeln können benutzt werden, wenn die geeignete Labormethode gegeben ist. Eine Hilfestellung mit Hintergrundinformation ist unter http://gfr.pedz.de gegeben um klinische Entscheidungsfindungen zu erleichtern.

Key words

renal function - cystatin C - GFR - glomerular filtration rate estimating equation - creatinine clearance - nephrotoxic substances

Schlüsselwörter

Nierenfunktion - Cystatin C - GFR - Schätzformeln glomeruläre Filtrationsrate - Kreatinin Clearance - nephrotoxische Substanzen

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