β crosslaps kit

The serum level of alkaline phosphatase (ALP) was measured using automated analysers. Other levels were measured using the following kits (all from Roche Diagnostics): a β‐CrossLaps kit for β‐CrossLaps of type I collagen containing cross‐linked C‐telopeptide (β‐CTX) and an osteocalcin kit for osteocalcin (OC). All serum biochemical parameters were measured in the central clinical laboratory of Shanghai Jiao Tong University Affiliated Sixth People's Hospital.

Blood samples were collected from fasting participants in the morning from 7:00 a.m. to 10:00 a.m., and serum aliquots were stored at −80°C until being assayed. Routine hepatic and renal functions, including ALP, ALT, AST, Cr, UA, and BUN, and serum calcium and phosphorus were measured using a cobas c 701 automatic biochemistry analyzer (Roche Diagnostic GmbH, Basel, Switzerland). All the bone metabolism markers were measured by electrochemiluminescence immunoassay with the following kits (Roche Diagnostic GmbH): total P1NP kit for procollagen type 1 N-propeptide (P1NP), β-CrossLaps kit for b-CrossLaps of type I collagen-containing cross-linked C-telopeptide (β-CTX), intact PTH kit for parathyroid hormone (PTH), and vitamin D total kit for 25-hydroxyvitamin D (25OHD). Serum ucOC was measured by ELISA using monoclonal mouse anti-Glu-OC as the capture antibody, peroxidase-labeled monoclonal mouse anti-OC as the detection antibody, and tetramethylbenzidine for chromogenic reaction (Glu-OC kit, Takara Bio Inc., Otsu, Japan). The intra- and interassay coefficients of variation (CVs) were 5.2% and 8.3%, respectively.

The serum levels of bone turnover markers, osteocalcin (OC) and β-CrossLaps (β-CTx), were determined by using the N-MID Osteocalcin kit (Cobas-Roche, Switzerland) and β-CrossLaps kit (Cobas-Roche, Switzerland), respectively. OC and β-CTx were analysed with the electrochemiluminescence immunoassay “ECLIA” and immunoassay analyser Elecsys 2010 (Hitachi High-Technologies Corporation, Tokyo, Japan) according to the manufacturers’ instructions.