1Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota

2Division of Clinical Trials and Biostatistics, Mayo Clinic, Rochester, Minnesota

3Department of Pathology and Medicine, Duke University, Durham, North Carolina

4Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota

5Department of Surgery and Immunology, Mayo Clinic, Rochester, Minnesota

6Department of Nephrology, Cleveland Clinic, Cleveland, Ohio

7Department of Urology, Mayo Clinic, Rochester, Minnesota

8Division of Epidemiology, Mayo Clinic, Rochester, Minnesota

aCorrespondence and offprint requests to: Andrew D. Rule, Mayo Clinic 200 1st St SW, Rochester, MN 55905, Phone: 507-284-6182, Fax: 507-284-1161, Email: [email protected]