Vascular calcification is a well-defined risk factor for cardiovascular disease and a-Klotho has been suggested to be an implicating factor in the process of vascular calcification, particularly in patients with chronic kidney disease (CKD).~With this study the investigators will examine the possible correlation of the levels of secreted a-Klotho with the severity of vascular calcification in the coronary arteries and aortic valve in patients with CKD at different stages of CKD. More precisely, a-Klotho was measured in 30 patients with end-stage renal disease under intermittent regular hemodialysis and 30 outpatients with stable CKD stage III (estimated glomerular filtration rate between 30 and 59 mL/min/1.73^2).~Participants in both groups were eligible only if stable for at least the last 3 months pre-enrollment. Calcification will be calculated using the well-established Agatston score after submitting all patients to multi-slice computed tomography.~Continuous variables will be described as median (25th-75th percentile) and categorical variables as N (%). Variables will be compared between groups using the non-parametric Mann-Whitney U test for continuous and Fisher's exact test for categorical variables. Bivariate correlations of a-Klotho levels with clinical variables and calcification scores using the Spearman correlation coefficient will be examined. Identification of a-Klotho determinants, log-transformation of a-Klotho levels was done because of log-normal distribution and stepwise linear regression was used, with probability to remove the variable>0.1. Identification of determinants of coronary and aortic calcification was done via log-transformation of the corresponding calcium scores, (a value of 0 was assumed; log-transformed-1 for absent calcium) and, stepwise linear regression was used as above. Because of the small sample size, all regression estimates, and confidence intervals were calculated with re-sampling so that robust variable selection and stable estimates can be ensured.
To define the correlation of the levels of a-Klotho with the severity of vascular calcification in the coronary arteries and aortic valve.