The association between mortality and abdominal aortic calcification and relation between its progression and serum calcium concentration in chronic hemodialysis patients

BACKGROUND The composite summary score (range, 0-24) of abdominal aortic calcification (AAC) devised by Kauppila et al is a simple method of assessing AAC severity. However, few studies have been conducted to determine an optimal AAC cutoff score for the prediction of mortality or to investigate the relation between mineral metabolism and AAC progression using the scoring system. METHODS The medical records of 112 patients on hemodialysis who had undergone simple lateral lumbar radiography every 6 months from August 2009 were reviewed. Patients were followed until November 2012, and the relationship between the degree of AAC at baseline and mortality was evaluated. In addition, the relationship between the progression of AAC and serum concentrations of calcium and phosphate was evaluated in the 75 patients who were successfully followed until November 2012. RESULTS The mean AAC score at baseline was 5.5±4.8, and the cutoff calcification score for the prediction of mortality was 7.75 (sensitivity=61%, specificity=81%). Patients were allocated to Group A (baseline total calcification score ≤8.0, n=85) or Group B (baseline total calcification score>8.0, n=27), and multivariate analysis showed that Group B was an independent risk factor of all-cause mortality and cardiovascular events. Of the 75 patients successfully followed, 51 showed AAC progression (Group 1) and 24 showed no change or improvement (Group 2). Group 1 was found to have significantly higher mean serum corrected calcium levels during the 2(nd) year and 3(rd) year of follow-up than Group 2. Furthermore, repeated-measures analysis of variance showed higher monthly corrected calcium concentrations (P=0.099) and mean corrected calcium levels during the 1(st) year, 2(nd) year, and 3(rd) year of follow-up (P=0.062) in Group 1, but without statistical significance. The cutoff values of mean corrected calcium of the 2(nd) year and 3(rd) year for the prediction of AAC progression during follow-up years were 8.96 mg/dL and 9.45 mg/dL, respectively. Serum phosphate levels and corrected calcium×phosphate values were similar in Groups 1 and 2. CONCLUSION Patients with an AAC score of>8 at baseline seem to be at higher risk of mortality during follow-up. Of the serum variables examined, such as corrected calcium, phosphate, and corrected calcium×phosphate, corrected calcium was found to be marginally associated with AAC progression. However, a larger-scale prospective study is required to confirm our findings.