[Radioimmunoassay for the pyridinoline cross-linked carboxy-terminal telopeptide of type 1 collagen (1CTP)--some basic aspects of the RIA kit and clinical evaluation in various bone diseases].

A radioimmunoassay for circulating levels of the pyridinoline cross-linked carboxy-terminal telopeptide of type 1 collagen (1CTP) was developed and can be available as a kit on a commercial base. Using the kits, we evaluated basically and clinically the assay. The assayed values were reproducible and the assay can detect as low as 0.5 ng/ml of 1CTP. In healthy volunteers, circulating level was high under age 24 and over age 46. In patients with bone metastasis, serum levels elevated even in its early stage and correlated well with clinical status. In other bone diseases, such as primary hyperparathyroidism, hyperthyroidism, post-gastrectomy, hypercalcemia of malignancy and myeloma, serum levels elevated according to their clinical conditions. In patients with chronic renal failure, serum levels were high, suggesting decrease of renal clearance of 1CTP. The circulating 1CTP levels seemed to reflect well clinical bone destructive status. A high correlation between serum 1CTP level and urinary pyridinoline (r = 0.884) was shown, whereas essentially no correlation was observed between bone formation markers such as osteocalcin and alkaline phosphatase. Thus, the measurement of circulating 1CTP seems to be a simple and sensitive method to monitor bone destruction.