Supplementary Material for: Coronary Artery Calcification in Hemodialysis and Peritoneal Dialysis

Background: Vascular calcification is seen in most patients on dialysis and is strongly associated with cardiovascular mortality. Vascular calcification is promoted by phosphate, which generally reaches higher levels in hemodialysis than in peritoneal dialysis. However, whether vascular calcification develops less in peritoneal dialysis than in hemodialysis is currently unknown. Therefore, we compared coronary artery calcification (CAC), its progression, and calcification biomarkers between patients on hemodialysis and peritoneal dialysis. Methods: We measured CAC in 134 patients who had been treated exclusively with hemodialysis (n = 94) or peritoneal dialysis (n = 40) and were transplantation candidates. In 57 of them (34 on hemodialysis and 23 on peritoneal dialysis), we also measured CAC progression annually up to 3 years and the inactive species of desphospho-uncarboxylated matrix Gla protein (dp-ucMGP), fetuin-A, osteoprotegerin. We compared CAC cross-sectionally with Tobit regression. CAC progression was compared in 2 ways: with linear mixed models as the difference in square root transformed volume score per year (ΔCAC SQRV) and with Tobit mixed models. We adjusted for potential confounders. Results: In the cross-sectional cohort, CAC volume scores were 92 mm3 in hemodialysis and 492 mm3 in peritoneal dialysis (adjusted difference 436 mm3; 95% CI –47 to 919; p = 0.08). In the longitudinal cohort, peritoneal dialysis was associated with significantly more CAC progression defined as ΔCAC SQRV (adjusted difference 1.20; 95% CI 0.09 to 2.31; p = 0.03), but not with Tobit mixed models (adjusted difference in CAC score increase per year 106 mm3; 95% CI –140 to 352; p = 0.40). Peritoneal dialysis was associated with higher osteoprotegerin (adjusted p = 0.02) but not with dp-ucMGP or fetuin-A. Conclusions: Peritoneal dialysis is not associated with less CAC or CAC progression than hemodialysis, and perhaps with even more progression. This indicates that vascular calcification does not develop less in peritoneal dialysis than in hemodialysis.背景：多数透析患者均可出现血管钙化（vascular calcification），且其与心血管死亡率密切相关。血管钙化可被磷酸盐所促进，而血液透析（hemodialysis）患者体内的磷酸盐水平通常高于腹膜透析（peritoneal dialysis）患者。然而，目前尚不明确腹膜透析患者的血管钙化发生率是否低于血液透析患者。为此，本研究对比了血液透析与腹膜透析患者的冠状动脉钙化（coronary artery calcification, CAC）情况、钙化进展程度及钙化生物标志物水平。 方法：本研究纳入134名仅接受血液透析（n=94）或腹膜透析（n=40）且符合肾移植候选标准的患者，对其冠状动脉钙化水平进行检测。其中57名患者（血液透析组34例、腹膜透析组23例）还接受了为期最长3年的年度随访，检测其冠状动脉钙化进展情况，以及脱磷酸未羧化基质Gla蛋白（desphospho-uncarboxylated matrix Gla protein, dp-ucMGP）、胎球蛋白-A（fetuin-A）与骨保护素（osteoprotegerin）的水平。研究采用Tobit回归对冠状动脉钙化进行横断面对比分析；冠状动脉钙化进展的对比采用两种分析方法：一是以线性混合模型分析每年平方根转换体积评分的差值（ΔCAC SQRV），二是采用Tobit混合模型进行分析。所有分析均对潜在混杂因素进行了校正。 结果：横断面队列分析显示，血液透析患者的冠状动脉钙化体积评分为92 mm³，腹膜透析患者为492 mm³（校正后差值为436 mm³；95%置信区间：-47~919；P=0.08）。纵向队列分析显示，以ΔCAC SQRV为评估指标时，腹膜透析患者的冠状动脉钙化进展程度显著更高（校正后差值为1.20；95%置信区间：0.09~2.31；P=0.03）；但采用Tobit混合模型分析时，该差异无统计学意义（校正后每年冠状动脉钙化评分升高差值为106 mm³；95%置信区间：-140~352；P=0.40）。腹膜透析患者的骨保护素水平更高（校正后P=0.02），但脱磷酸未羧化基质Gla蛋白与胎球蛋白-A水平无组间差异。 结论：与血液透析相比，腹膜透析患者的冠状动脉钙化及钙化进展程度并未更低，甚至可能更高。这表明腹膜透析患者的血管钙化发生率并不低于血液透析患者。