The combined prognostic significance of alkaline phosphatase and vascular calcification in patients with end-stage kidney disease

Background and aims: Little is known about the interaction between serum alkaline phosphatase (ALP) and vascular calcification (VC) affecting cardiovascular events (CVE) and mortality in end-stage kidney disease (ESKD) patients. This study investigated the combined effect of ALP and VC on prognosis in ESKD patients starting dialysis. Methods and results: Data from 587 ESKD patients treated at a single center between January 2006 and July 2017 were retrospectively evaluated. VC was assessed by the aortic calcification index (ACI) using abdominal computed tomography. Patients were stratified into four groups according to the median ACI (17.18) and serum ALP value (108.0 U/L) as low ACI-low ALP, low ACI-high ALP, high ACI-low ALP, or high ACI-high ALP. The association between ALP and VC and the composite of CVE and death was analyzed. During a median follow-up of 3.1 years (range, 1.5–5.6 years), 140 patients (23.8%) developed CVE and 130 deaths (22.1%) occurred. In the stratified analysis, patients with high ACI-low ALP had a greater risk of the composite endpoint than patients with low ACI-low ALP (adjusted hazard ratio, 2.09; 95% confidence interval, 1.58–2.60; P = 0.004). Patients with high ACI-high ALP had the greatest risk (adjusted hazard ratio, 2.25; 95% confidence interval, 1.77–2.72; P = 0.001). The interaction between ACI and ALP on CVE and mortality was statistically significant (P < 0.05). Conclusions: The combined effect of VC and higher ALP was associated with a greater risk of CVE and death, and high serum ALP amplified the risk associated with VC in ESKD patients starting dialysis.