[Analysis of the levels of serum total calcium and inorganic phosphate of 2,342 children in Beijing].

OBJECTIVE: To study the changes of serum total calcium (Ca) and inorganic phosphate (P) levels during children growth and related factors. METHODS: Using a stratified-multi-steps-cluster sampling method, we selected 2,342 healthy children aged 10-18 years from urban and suburban areas of Beijing from September 2001 to December 2001 to test the levels of serum Ca and P. Their meal status was also surveyed to analyse the correlation of the leves of serum Ca and P with sex, age, height, weight, and diet on statistic basis. RESULTS: The Ca levels of Beijing children were (2.39 +/- 0.12) mmol/L, which had a positive correlation with age, height, and weight (P < 0.01). The Ca levels of female children were somewhat higher than those of male [male, (2.38 +/- 0.12) mmol/L; female, (2.39 +/- 0.12) mmol/L; P < 0.05]. The Ca levels of urban children were significantly higher than those of suburban children [urban, (2.40 +/- 0.13) mmol/L; suburban, (2.37 +/- 0.10) mmol/L; P < 0.001]. The P levels of Beijing children were (1.39 +/- 0.18) mmol/L, which had a negative correlation with age, height, and weight (P < 0.01). The P levels of male children were significantly higher than those of female [male, (1.43 +/- 0.18) mmol/L; female, (1.36 +/- 0.17) mmol/L; P < 0.001]. The P levels of urban children were significant higher than those of suburban children [urban, (1.41 +/- 0.19) mmol/L; suburban, (1.38 +/- 0.16) mmol/L; P < 0.001]. The Ca levels of Beijing children had a negative correlation with P levels (r=-0.141, P < 0.01). [Ca] x [P] (mmol/L) of Beijing children were 3.32 +/- 0.44. The value of [Ca] x [P] reached peak by 3.45 +/- 0.46 when Beijing children were of 13-14 years old, and then the value declined with increasing age. CONCLUSION: The levels of serum Ca and P correlates with sex, age, growth, and diet. The level of serum Ca goes up while P goes down during the children growth.