Establishment of Reference Intervals for Bone Markers in Children and Adolescents

Objectives: To determine age and gender specific reference intervals for bone markers.

Design And Methods: Morning blood samples were collected after overnight fast from 356 healthy children (6 to 18 year-old) for the determination of bone marker levels, PTH and vitamin D(3). Multiple regression analysis was done to assess the effect of factors that could influence the bone marker levels; the central 95% reference interval and their 90% CI were calculated.

Results: After excluding samples when BMI-z -scores were <-2 or >+2, both vitamin D(3) and PTH levels were abnormal and from children who used steroids the remainder were partitioned using Tanner stage based chronological age. As expected the reference intervals show a significant variation with age and gender. All the bone marker levels, except total alkaline phosphatase, were significantly higher in puberty with vitamin D(3) >75nmol/L.

Conclusion: Vitamin D status, age and gender are important for establishing reference intervals of bone markers in healthy children.