Normal values for urine renalase excretion in children.
BACKGROUND
The objective of this study was to establish age-dependent values for urinary renalase/creatinine (renalase/Cr) ratio in healthy children and adolescents.


METHODS
The study was conducted on a random sample of 157 healthy children and adolescents (0.1-17.9 years) divided into six age groups in 3-year intervals. Urine renalase concentration was measured using an enzyme-linked immunosorbent assay (ELISA) kit (Uscn Life Science, Wuhan, China).


RESULTS
We analyzed median urine renalase/Cr ratio in particular age groups with the use of analysis of variance (ANOVA). Renalase/Cr levels were significantly higher in the youngest children < 3 years in comparison with other age groups (4.07 ng/mg Cr, p < 0.05). There was a statistically significant negative correlation between urine renalase/Cr and body mass index (BMI) Z-score (r = -0.22, p < 0.05) and both systolic (r = -0.22, p < 0.05) and diastolic (r = -0.21, p < 0.05) blood pressure. We constructed the reference renalase/Cr percentiles according to age in 3-year intervals.


CONCLUSIONS
To the best of our knowledge, this study is the first to present reference values of urine renalase excretion in a healthy pediatric population. Further studies should concentrate on the influence of increased blood pressure or obesity on urine renalase excretion in children and teenagers.