Objectives: To obtain normative reference values for urinary calcium excretion in Chinese adolescents.
Methodology: A random group of 425 healthy Chinese adolescents aged 12-19 years were recruited from secondary schools in Hong Kong. Each subject provided a sample of morning urine for the assessment of calcium and creatinine excretion. A subgroup of 80 subjects provided a 24-h urine sample for assessment of daily calcium excretion.
Results: The mean (+/-S.D.) and median urinary calcium/creatinine concentration ratios (UCa/Cr) expressed in mmolmmol creatinine were 0.18 (+/-0.16) and 0.12. Girls had a higher UCa/Cr than boys (P < 0.0001). The mean+/-S.D. 24-h urinary calcium excretion was 0.043+/-0.025 mmol kg day(-1) (1.71+/-1.01 mg kg day(-1)).
Conclusion: The UCa/Cr ratio and 24-h urinary calcium excretion are low when compared with published values for Caucasian children. The apparent rarity of nephrolithiasis and microscopic haematuria associated with hypercalciuria may be related to the low urinary calcium excretion in this population.