Normal Value of Random Urinary Calcium to Creatinine Ratio in Children in Zahedan, South-East of Iran

Background: Random urine calcium/creatinine ratio (UCa/Cr) is used practically for the screening of hypercalciuria. Objectives: This study aimed to determine the age-specific reference value of UCa/Cr and its relationship with urinary Na/K in children in Zahedan, South-East of Iran. Methods: In a cross-sectional study, UCa/Cr and UNa/K ratios were measured in non-fasting morning urine samples of 1,506 randomly selected primary school children. Results: The prevalence of hypercalciuria was 3.1%, with no significant difference between males and females. Mean UCa/Cr was 0.09 ± 0.21, and the 95th percentile was 0.27 and 0.22 in seven and 12-year-old children, respectively. Mean urinary UNa/UK was 2.90±1.89, and the 95th percentile was 7.83 and 10.57 in seven and 12-year-old children, respectively. The correlation between UCa/Cr and UNa/UK was statistically significant (r=0.128, P < 0.001). There was also a positive correlation between UCa/Cr and UNa/UK, especially in seven-year-old children (r=0.508, P < 0.001). Conclusions: Different reference values of UCa/Cr for seven and 12-years-old emphasize that age-specific reference values of UCa/Cr should be established for each population to be used as a screening method for hypercalciuria.