MO734: High Serum Oxalate Concentration Associated with Coronary Artery Calcification and Lanthanum Carbonate in Hemodialysis Patients

Abstract

BACKGROUND AND AIMS Oxalate is an organic acid found in abundance in plants and can also be synthesized as a terminal metabolite by the organic acid metabolism systems in humans. As a major excretion pathway of oxalate is urine, serum oxalate (SOx) concentration elevates in end-stage renal disease (ESRD) patients and causes calcium oxalate deposition to tissues. We previously reported that calcium oxalate might be one of the major components of coronary artery calcification (CAC) in ESRD patients; however, the association between SOx and CAC is unknown. This study aimed to demonstrate the relationship between SOx and CAC in haemodialysis patients. METHOD A total of 77 patients undergoing maintenance haemodialysis at a single facility who underwent an atherosclerosis check-up from 2011 to 2012 were enrolled and measured SOx retrospectively in 2021. Of those, 17 extremely outlying SOx patients were excluded, and 60 patients including 42 males were analysed. The median age was 64 (35–85) years, and median dialysis duration was 87.5 (17.1–410) months. Gender, Agastston's CAC score, major artery calcification volume, laboratory data and medications around the atherosclerosis check-up date and new-onset cardiovascular disease (CVD) events and deaths during the 10-year observation period were recorded. A CVD event is defined as an admission due to non-fatal myocardial infarction, coronary artery disease or heart failure. SOx level was measured by the commercial colorimetric oxalate assay kit, and the normal SOx level was 181 µmol/L. RESULTS The median SOx was 267 (221–563) µmol/L and new-onset CVD events, all-cause deaths occurred in 28 (47%) and 22 (37%) patients, respectively. In univariate analysis, SOx was associated with males (r = 0.27, P = 0.03), serum albumin (r = –0.25, P = 0.05), uric acid (r = 0.29, P = 0.02), phosphate (r = 0.26, P = 0.04), alkaline phosphatase (r = –0.28, P = 0.03), lanthanum carbonate (r = 0.32, P = 0.01), major artery calcification volume (r = 0.28, P = 0.03) and CAC score (r = 0.29, P = 0.02). In multivariate regression analysis, SOx was associated with lanthanum carbonate (F = 5.96, P = 0.02) and CAC score (F = 4.47, P = 0.03, Table 1). Receiver operating characteristic curve showed SOx = 269.5 µmol/L was the best cut-off for predicting CVD events. We divided subjects into two groups by this cut-off SOx value and revealed SOx was associated with new-onset CVD events (N = 60, P = 0.01) even after adjusted by age under 75 years (N = 52, P = 0.03) or both age under 75 years and CAC score under 1000 (N = 28, P = 0.04) by the Kaplan–Meier method (Fig. 1). CONCLUSION SOx was associated with CAC score, lanthanum carbonate and CVD events in ESRD patients undergoing haemodialysis.