Biochemical evaluation of bone metabolism in dialysis patients

Chronic renal failure (CRF) patients are prone to develop bone diseases. Se rum bone alkaline phosphatase (BAP) is a good marker for bone formation in these patients. There is no equivalent serum test to evaluate their bone re sorption, but serum pyridinoline (PYD) and deoxypyridinoline (DPYD) crossli nks could be a valid alternative to the urine test? which is not useful in CRF. Bone metabolism was evaluated in 36 dialyzed patients by measuring PYD and DPYD with HPLC, and BAP with electrophoresis at 3 - 5 occasions within a 4- to 9-month interval. PYD ranged from 46 - 1666 nmol/l and DPYD from 6 - 475 nmol/l. Median intra-individual CVs were 13% for PYD, 21% for DPYD a nd 19% for BAP. DPYD correlated strongly with PYD. PYD, DPYD and BAP correl ated negatively with age. PYD and DPYD strongly correlated with BAP. PYD, D PYD and BAP correlated with PTH. BAP < 16 U/l and PTH > 200 ng/l were used as biochemical criteria for adynamic bone disease (low bone turnover) and s econdary hyperparathyroidism (high bone turnover), respectively. Implementa tion of the values with optimal diagnostic performance (ROC curves) allowed to discriminate between low and high bone turnover in individual dialysis patients.