These aims are examined in a prospective cohort study (of incident HD patients living throughout the US (>1000 centers) with detailed demographic data updated daily, and research quality blood samples collected every 3 months from the initiation of chronic HD. We initiated this "USRDS-like" study to overcome one of the largest limitations of existing epidemiological dialysis datasets – lack of concomitant biological samples in a nationally representative cohort. The study will be available for data sharing and patient protection measures are in place.