Tamara van Donge

Kidney injury biomarkers in pediatrics 179 9 n=81 n=40 n=28 n=63 n=676 1 study 2 studies 1 study 1 study 2 studies 0 100 200 300 400 Preterm neonates Term neonates Infants & toddlers (girls) Infants & toddlers (boys) Children & adolescents Mean uNGAL (ng/mL) Figure 3: Means for urinary NGAL values retrieved from literature 18,29,30,32 for different age groups; preterm neonates (<1 month, <37 weeks gestational age), term neonates (<1 month, >37 weeks gestational age), infants and toddlers (>1 month, <3 years), and children and adolescents (>3 years, <20 years). Cystatin C Cystatin C is a low weight protein that is produced at a constant rate and freely filtered by the glomerulus, and reabsorbed and catabolized by the proximal tubular epithelial cells. 20 Cystatin C can be measured in urine and blood. Serum cystatin C is not affected by physiological variables such as muscle mass, and is therefore a more suitable biomarker for kidney function or glomerular filtration rate. 8 Another advantage of serum cystatin C, in contrast to serum creatinine, is that serum cystatin C is not transferred over the placenta, and therefore can be used as a marker in the first days of life after birth. It was found that serum cystatin C concentrations were highest in neonates (preterm and term) and declined with age, until approximately one year of age, when adult values are reached. 33,34 Analogous to urinary NGAL, significant differences in urinary cystatin C values between preterm neonates, based on their gestational age are observed. Higher mean urinary cystatin C values (1354 ng/mL) are observed in extremely preterm neonates (<26 weeks gestational age), compared to preterm neonates of ≥30 weeks gestational age (209 ng/mL). 29 Finney et al . showed similar results with mean plasma cystatin C values of 1480 ng/mL for extremely preterm neonates and mean plasma cystatin