Chinese Bone Turnover Marker Study: Reference Ranges for C-Terminal Telopeptide of Type I Collagen and Procollagen I N-Terminal Peptide by Age and Gender

BACKGROUND Bone formation marker procollagen I N-terminal peptide (PINP) and resorption marker C-terminal telopeptide of type I collagen (β-CTX) are useful biomarkers for differential diagnosis and therapeutic evaluation of osteoporosis, but reference values are required. METHODS The multi-center, cross-sectional Chinese Bone Turnover Marker Study included 3800 healthy volunteers in 5 Chinese cities. Serum PINP, β-CTX, parathyroid hormone (PTH) and 25OHD levels were measured by chemiluminescence assay. Lumbar spine and proximal femur BMD were measured by dual-energy X-ray absorptiometry. Serum PINP and β-CTX levels were assessed by age, gender, weight, recruitment latitude, levels of PTH and 25OHD. RESULTS Subjects (n = 1436, M:F, 500:936; mean age 50.6 ± 19.6 years) exhibited non-normally distributed PINP and β-CTX peaking between 15-19 years, gradually declining throughout adulthood, elevating within 10 years of postmenopause, and then declining by age 70. In women between the age of 30 and menopause, median PINP and β-CTX levels were 40.42 (95% CI: 17.10-102.15) and 0.26 (95% CI: 0.08-0.72) ng/mL, respectively. β-CTX and PINP were positively linearly correlated (r = 0.599, P<0.001). β-CTX correlated positively (r = 0.054 and 0.093) and PINP correlated negatively (r =  -0.012 and -0.053) with 25OHD and PTH (P<0.05). CONCLUSIONS We established Chinese reference ranges for PINP and CTX. Chinese individuals exhibited high serum PINP and β-CTX levels between 15 and 19 years of age and at menopause, which gradually declined after 70 years of age.