2. Subjects with known intrinsic renal disease (e.g., a urine protein/ creatinine ratio > 150 mg/g or the presence of an abnormal number of red blood cells (RBCs) or granular casts in the urine) AND calculated GFR < 40 ml/min/1.73 m^2 body surface area (BSA) (abbreviated Modification of Diet in Renal Disease [MDRD]). Subjects must have a calculated GFR assessment within 1 month prior to enrollment.