Higher serum bone alkaline phosphatase as a predictor of mortality in male hemodialysis patients

Aims: Higher serum alkaline phosphatase predicts lower mortality in chronic kidney disease and hemodialysis patients without liver dysfunction because it reflects high bone turnover. The purpose of our study was to compare the significance of serum bone alkaline phosphatase (BAP) with that of other bone markers in prediction of all-cause mortality(ACM) in male hemodialysis patients.

Main methods: The study was performed for 5 years. Serum BAP, intact osteocalcin (iOC), ß-CrossLaps (CTX), and intact parathyroid hormone (iPTH) were measured in 196 male hemodialysis patients without radiographic fracture. Their day-to-day variation during 5 consecutive days and diurnal variation were determined in 13 healthy males.

Key findings: The patients were divided into higher and lower groups based on serum levels of bone markers(mean±SD: iPTH 218.6±214.5 pg/ml, BAP 23.6±12.2 U/L, iOC 42.8±45.2 ng/ml, CTX 1.71±1.23 nmol/L BCE). In Kaplan-Meier analysis, the higher BAP group had significantly higher ACM than the lower BAP group (P=0.013), whereas mortality did not differ between the higher and lower groups in other markers. Cox regression hazard analysis identified higher log BAP as a significant independent predictor [hazard ratio(HR) 8.32(95%CI:1.18-58.98)] for ACM after adjustment for various factors including pre-existing cardiovasucular disease, presence of DM. The significant association of mortality with serum BAP alone, in contrast with other markers including CTX [HR0.64 (95%CI:0.16-2.47)], iOC [HR0.97(95%CI:0.36-2.64)], iPTH [HR0.84(95%CI:0.44-1.60)], it may be due to the narrower day-to-day variation and the absence of diurnal variation in serum BAP compared to other markers.

Significance: Higher serum BAP may be a predictor of ACM in male hemodialysis patients.