Relationship Between Bone-Specific Alkaline Phosphatase And Cardiovascular Calcification In Maintenance Hemodialysis Patients

Objectives: 1)To investigate the prognostic value of abdominal aortic calcification(AAC)in maintenance hemodialysis(MHD)patients.2)To observe the levels of serum bone-specific alkaline phosphatase(BAP)in MHD patients and its influencing factors.3)To examine the relationship between serum BAP levels and cardiovascular calcification in MHD patients.Methods: 1)164 patients undergoing MHD were enrolled.Abdominal lateral plain radiograph was used to detect the calcification of abdominal aorta.These patients were divided into low AAC group(AAC?4)or high AAC group(AAC>4)according to the AAC score,and followed up over a period of 54.39±13.90 months.Kaplan-Meier analyses were performed to compare the all-cause and cardiovascular mortality between the two groups.Cox proportional hazards analyses were performed to identify the factors associated with all-cause and cardiovascular mortality.Receiver operating characteristic(ROC)curves and areas under curves(AUC)were used to evaluate the prognostic value of AAC for MHD patients.2)Serum BAP levels in 156 MHD patients and 30 age and sex matched controls were measured by using ELISA.Stepwise multiple linear regression was used to analyze the risk factors influencing the serum BAP levels in MHD patients.3)Abdominal lateral X plain and ultrasonic cardiogram were used to evaluate the AAC and valvular calcification in 156 MHD patients.The relationship between serum BAP levels and cardiovascular calcification in MHD patients were studied.Results:1)The prevalence of AAC in this cohort was 68.90%.Kaplan-Meier analyses showed that all-cause(31.65% vs 8.24%,P < 0.01)and cardiovascular mortality(22.78% vs 4.71%,P<0.01)were significantly higher in high AAC group compared to low AAC group.Cox proportional hazards analyses found that AAC was an independent risk factor for all-cause(HR=3.057,95%CI:1.051-8.890,P=0.012)and cardiovascular mortality(HR=4.263,95%CI:1.239-10.268,P=0.003).ROC curves showed that AAC was associated with a higher predictive value for all-cause and cardiovascular mortality.The AUC were 0.719(95%CI: 0.617-0.821,P<0.01)and0.743(95%CI: 0.640-0.847,P<0.01)respectively.2)Serum BAP levels in MHD patients were significantly higher than those in healthy controls [19.75(17.45-21.90)?g/L vs 11.75(8.85-12.98)?g/L,P<0.01].The levels of serum BAP were positively related with duration of dialysis(r=0.166,P=0.031)?high-sensitive C-reactive protein(hsCRP)(r=0.156,P=0.045)?intact parathyroid hormone(iPTH)(r=0.218,P=0.004)and AAC score(r=0.389,P=0.001).Stepwise multiple linear regression showed iPTH(?=0.208,P=0.005)and AAC(?=0.231,P=0.002)were independent risk factors influencing the serum BAP levels in MHD patients.3)Serum BAP levels were significantly higher in severe AAC patients(AAC?16)than those without or mild AAC patients(AAC ?4)[21.40(20.45-23.60)?g/L vs 17.30(16.20-19.50)?g/L,P<0.01] and moderate AAC patients(5 ? AAC ? 15)[21.40(20.45-23.60)?g/L vs19.80(17.80-21.90)?g/L,P < 0.01].Serum BAP levels were significantly higher in patients with valvular calcification compared to those without valvular calcification[21.05(19.25-23.30)vs 18.60(16.95-21.20),P<0.01)].With the increase of serum BAP levels,the proportion of severe AAC patients increased gradually and the proportion of mild AAC patients decreased gradually.The levels of serum BAP were positively related with left ventricular end-diastolic diameter(LVDd)(r=0.218,P=0.014)?left ventricular end-systolic diameter(LVDs)(r=0.251,P=0.005)and left atrial diameter(LAD)(r=0.273,P=0.002),and negatively related with left ventricular ejection fraction(LVEF)(r=-0.026,P=0.006).Multivariate Logistic regression analysis showed that age(OR=2.527,P=0.012)? duration of dialysis(OR=3.025,P=0.023)and serum BAP levels(OR=3.475,P=0.026)were independent risk factors of AAC in MHD patients.ROC curves showed the AUC of the serumBAP in the diagnosis of AAC was 0.737(95%CI: 0.619-0.855,P=0.001)with the sensitivity of 81.7% and specificity of 74.5% for a cutoff value of 17.55.Conclusions: The prevalence of AAC was high in MHD patients.The all-cause and cardiovascular mortality were significantly higher in patients with severe AAC.AAC might predict the poor prognosis in MHD patients.Serum BAP levels in MHD patients were significantly higher than those in healthy age and sex matched controls.AAC and iPTH were independent risk factors influencing the BAP levels in MHD patients.Serum BAP levels might be associated with cardiovascular calcification in MHD patients.