SP289FACTORS ASSOCIATED WITH VASCULAR CALCIFICATION IN CKD: BASELINE ASSESSMENTS FROM A CLINICAL TRIAL

Abstract

INTRODUCTION AND AIMS: Vascular calcification is common in chronic kidney disease (CKD), vascular disease and diabetes, and is associated with increased cardiovascular morbidity and mortality. Vascular calcification is thought to increase as CKD progresses, in association with development of CKD mineral and bone disorder. Vascular calcification can be quantified from plain lateral lumbar x-rays. Using baseline data from a clinical trial of vitamin K supplementation (K4Kidneys: ISRCTN21444964), we assessed factors associated with vascular calcification in patients with CKD stage 3b and 4. METHODS: Patients from a single centre participating in the K4Kidneys trial were included. Vascular calcification was estimated from lateral lumbar x-rays taken at the baseline trial visit. An overall vascular calcification score was determined independently by two authors according to the severity of calcific deposits in the aortic wall adjacent to L1-L4 vertebrae (the Kauppila method). The average total vascular calcification score was used for analysis. Demographic and baseline biochemical data were extracted from the electronic patient record. Multiple linear regression analysis was conducted to identify factors associated with vascular calcification score. The intra-class correlation coefficient was used to determine inter-observer agreement on vascular calcification score. Analyses were conducted using stats and Hmisc packages for R statistical software package. RESULTS: There were 122 patients with CKD 3b and 4 included in the analysis: 72 (59%) were male and average age was 65 years. Seventy-three (59.8%) patients with vascular calcification (vascular calcification score > 1) were older (70 vs 58 years) with higher systolic blood pressure (142 vs 135 mmHg). Those with vascular calcification had more pre-existing vascular disease (67.1 vs 40.8%) but similar proportion of diabetes (27.4 vs 28.6%). Duration (median 7.2 vs 7.0 years) and severity (CKDEPI 29.3 vs 29.5 ml/min) of CKD were similar. There were no significant differences in calcium, phosphate, albumin, parathyroid hormone, log urine protein:creatinine ratio or body mass index. On multiple linear regression analysis, factors associated with vascular calcification score were higher age at lateral lumbar x-ray (OR 0.16 per year increase in age; p<0.001), lower body mass index (OR-0.21 per unit increase in kg/m2; p=0.02), higher systolic blood pressure (OR 0.10 per unit increase in mmHg; p=0.001) or history of vascular disease (OR 2.5; p=0.01). Intra-class correlation coefficient for vascular calcification score (2 raters) was 0.94 (95% CI 0.92-0.96). CONCLUSIONS: In patients with CKD stage 3b/4, vascular calcification score was associated with increased age and systolic blood pressure, lower body mass index, history of vascular disease, but not with duration or severity of CKD or traditional markers of disordered mineral and bone metabolism. These offer few specific targets for intervention to slow development of vascular calcification in patients with CKD. Other remediable factors-including vitamin D/K status and activity of calcification inhibitors-are likely to be important in this group and warrant further study.