The Study Of Normal Urinary Calcium/Creatinine Ratios In 0～18 Children Of Tianjin City

Objective A random urinary calcium/creatinine ratio (UCa/Cr)is of practical use in screening for hypercalciuria. In several civial cities the reference values of UCa/Cr for children have been established.No study has been conducted to establish normal UCa/Cr values for healthy children of Tianjin city. Moreover ,these studies did not show that UCa/Cr varied with age in our country.However, recent studies have shown that UCa/Cr varies with ages in other countries. It has also been previously reported that an elevated UCa/Cr is related to a high urine Na/K ratio (UNa/K). The objective of the present study is :(1) to set up normal UCa/Cr by age in the pediatric population of Tianjin city. (2) to identify how the factor of age influences the variation of the UCa/Cr ratio. (3) to study the relationship between UCa/Cr and UNa/K in healthy children .Methods: A total of 525 healthy children of both gender (271 male ,254 femal) ranging in age from 1 day to 18 years were enrolled in the study after a questionnaire relative to the family's medicalhistory and diseases history were completed by their parents . They were devided into four age groups as follows : (1)<7 months (2) 8-18months (3) 19 months to 7 years and (4) 8-18 years.Children were told not to change their eating habits or physical activities. Random,non-fasting urine sample were obtained from each subject using urine bags or cups depending on the children's age. These urine samples were prevented at low temperature. The UNas UK^ UCa UCr concentrations were measured in three hours.The UNa UKUCa and UCr concentrations were measured with a Beckman CX3 electrolyte analyzer. Ratios between UCa/Cr,UNa/K,UNa/Cr and UK/Cr were calculated for each subject. The data analyses were performed using SPSS Version 10.0 For Windows.Results The age-dependent 95th percentiles of UCa/Cr values for Tianjin healthy children are (1) (1 months 0.78 (2) 8-18months 0.56 (3)19 months to 7 years 0.26 and(4)8 -18 years 0.20. We also find a inverse relationship between UCa/Cr and age Lg(UCa/Cr)=-0.95-0.20Lg(Age)(r=-0.33,b=-0.20,p<0.01).The relation- ship between UCa/Cr and UNa/K is found to be extremelyweak in Tianjin healthy children (r=0.03, p>0.01) .On the other hand,a linear correlation is observed between UNa/K and age(r=0.31,p<0.01)0Conclusions We conclude that the children's age should be take into consideration when assessing UCa/Cr ratio.We have established the reference values of UCa/Cr for Tianjin healthy children at different ages.Contrary to what has previously been reported in hypercalciuric children, no significant relationship is found between UCa/Cr and UNa/K in healthy children. We find significant relationship between UCa/Cr and UK/Cr,no significant relationship between UCa/Cr and UNa/Cr.