Anticipated Results: We anticipate that prolonged (1 year) management of PTH levels using a second generation of PTH assays will lead to an increase in the total administered dose of vitamin D analogues. Moreover, this increase in vitamin D administration will result in increased coronary calcification at the end of one year of therapy. Conversely, maintaining a 1-84/7-84 PTH ratio between 1.4-1.6 using the Scantibodies third generation assay will reduce the amount of administered vitamin D analogues and subsequently reduce the amount of coronary calcification at one year.