Abstract: Objective To analyze the serum calcium, phosphate and alkaline phosphatase level among apparently healthy school children and adolescents in Heilongjiang Province and establish the reference intervals in different gender and different age groups. Methods Random sample of 2101 primary and secondary school students from 9 to 18-year-old was selected from different district of Heilongjiang Province including Harbin and Mudanjiang from July 2008 to June 2009. The fasting venous blood was collected and serum calcium, phosphate and alkaline phosphatase concentration was measured as soon as possible. After screening outlier individual, a total of 2091 subjects were enrolled. The reference intervals of serum calcium, phosphate and alkaline phosphatase for healthy school children and adolescents were established by gender and age (P2.5 to P97.5). Results The change tendency of serum calcium, phosphate and alkaline phosphatase with age and sex were presented. All these parameters had shown inverse relationship with age and were significantly higher in boys than girls (P<0.001). Serum calcium, phosphate of both sexes and serum alkaline phosphatase of girls declined progressively with age. However, the highest alkaline phosphatase level was seen at 13 years in boys. Alkaline phosphatase showed a positive correlation with age before 13 years of age, but after that alkaline phosphatase started to decline. Conclusion Reference intervals of serum calcium, phosphate and alkaline phosphatase for healthy school children and adolescents in Heilongjiang Province in the age group of 9–18 years were presented, which supply good reference value for clinicians, especially pediatricians to interpret the results of school children and adolescents and make decision.

Key words: Healthy school children and adolescents, calcium, phosphate, alkaline phosphatase, Reference interval