Normal Values for Random Urinary Calcium to Creatinine Ratio in Iranian Children

Objective: Due to worldwide variations, reference values of urinary calcium to creatinine ratio in pediatric population are not yet well established. To determine normal values for urinary calcium to creatinine ratio and its relation to urinary sodium or potassium, a descriptive (correlation type) study was conducted in 7 to 12 years old healthy children in Urmia, Iran.
Methods: Primary school children were divided into two sectors and 7 clusters (4 cluster school boys and 3 school girls). The subjects were randomly selected. Random, non–fasting morning urine samples were obtained from 364 healthy children aged 7 to 12 years during fall 2005 and immediately sent to laboratory to determine urine calcium (Uca), creatinine(Cr), sodium (Na) and potassium (K). For data analysis, mean and 95th percentile of UCa/Cr and UNa/K were used. Pearson test was used to determine any relationship between UCa/Cr and UNa/K values. For comparison of UCa/Cr and UNa/K values between males and females, Mann-Withny test was used.
Findings: A total number of 364 children were enrolled in the study. There were 208 (57.1%) males and 156 (42.9%) females. The mean and 95th Percentile for UCa/Cr was 0.11 ( 0.10 and 0.24 respectively. The mean and 95th percentile for UNa/K were 2.30 ( 1.42 and 5.21 respectively. There was no significant difference in UCa/Cr and UNa/K between two sexes (P>0.05). We found a weak relationship between UCa/Cr and UNa/K (P<0.01).
Conclusion: UCa/Cr value may differ according to geographic location. For screening purposes, reference values should be determined in each geographic location.

Keywords
Urinary calcium; Urinary creatinine; Hypercalciuria; Urinary sodium; Urinary potassium