Age-related reference intervals for bone turnover markers from an Australian reference population.

BACKGROUND This study was performed to establish age-related serum reference intervals for procollagen type I N-propeptide (P1NP) and type I collagen C-telopeptide (CTx) in the Australian population. METHODS Fasting sera from 1143 males (mean age 60 years; range 20-97 years) and 1246 females (mean age 53 years; range 20-93 years) who participated in the Geelong Osteoporosis Study were analysed for CTx and P1NP using the automated Roche Modular Analytics E170 analyser. RESULTS Optimal age-related reference intervals were based on the central 90% of the distribution. The male CTx reference interval was divided into three age groups. For men aged 25 to 40 years, the interval was 170-600 ng/L; 40 to 60 years, the interval was 130-600 ng/L; and for men aged greater 60 years the interval was 100-600 ng/L. For P1NP the male reference interval was 15-80 μg/L for men aged between 25 to 70 years. In men greater than 70 years of age values were higher possibly due to increased bone turnover. High values are frequently seen for both CTx and P1NP in males aged younger than 25 years. This is probably due to bone growth that is not completely finalised. The female CTx reference interval was divided into four age groups. For women aged less than 30 years, the interval was 150-800 ng/L; 30-39 years, the interval was 100-700 ng/L; 40-49 years, the interval was 100-600 ng/L; and for women aged 50 years or more the interval was 100-700 ng/L. The female P1NP reference interval was divided into four age groups. For women aged less than 30 years, the interval was 25-90 μg/L; 30-39 years, the interval was 15-80 μg/L; 40-49 years, the interval was 15-60 μg/L; and for women aged 50-69 years the interval was 15-75 μg/L. In women greater than 70 years of age values were higher possibly due to increased bone turnover. CONCLUSION Values obtained from this large study provide sound age-related reference intervals for serum P1NP and CTx values in the Australian population.