Body mass does not have a clinically relevant effect on cystatin C eGFR in children.
BACKGROUND
Unlike creatinine, Cystatin C (CysC) is believed to be independent of body composition in both adults and children. Recent findings in adults, suggesting an improved performance of CysC-based estimated glomerular filtration rate (CysC eGFR) by accounting for body mass, necessitated a careful re-evaluation of this issue in children.


METHODS
We studied 240 children (median age 11.7 years, range 2-17.9 years, 107 girls), with various kidney diseases, for any change in the relationship between (99)Tc DTPA GFR and CysC eGFR after accounting for body mass. For body mass assessment, body mass index (BMI) z-score was calculated using height-adjusted age, to account for growth retardation secondary to chronic kidney disease.


RESULTS
CysC eGFR did not have a significant correlation with BMI z-score (correlation coefficient = 0.06; P = 0.34). Accounting for BMI z-score did not add to the 65% variance in nuclear GFR explained by CysC eGFR. Moreover, it did not change the regression coefficient of 0.85 between CysC eGFR and nuclear GFR either. On Bland & Altman analysis, the bias of 0.05 and standard deviation of 20.39 also did not improve after accounting for BMI z-score in the revised CysC eGFR formula.


CONCLUSIONS
In children, body mass exerts a minimal effect on the performance of CysC eGFR estimation.
Sharma
Ajay P
AP
Department of Paediatrics, Division of Paediatric Nephrology, Children's Hospital, London Health Science Centre, University of Western Ontario, London, Canada.
Kathiravelu
Anusha
A
Nadarajah
Renisha
R
Yasin
Abeer
A
Filler
Guido
G
D000293:Adolescent; D015415:Biomarkers / Q000378:metabolism; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D055316:Cystatin C / Q000378:metabolism*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007674:Kidney Diseases / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D008297:Male; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D016284:Technetium Tc 99m Pentetate
D015415:Biomarkers; D055316:Cystatin C; D019275:Radiopharmaceuticals; D016284:Technetium Tc 99m Pentetate