1. Renal-Electrolyte and Hypertension Division; Department of Medicine; Center for Clinical Epidemiology and Biostatistics; University of Pennsylvania School of Medicine; Philadelphia; PA; USA
2. Division of General Medical Sciences; Department of Medicine; Washington University School of Medicine; St. Louis; MO; USA
3. Renal and Pancreas Transplant Division and Division of Nephrology, Department of Medicine; Saint Barnabas Medical Center; Livingston; NJ; USA
4. Department of Epidemiology; School of Public Health; University of Medicine and Dentistry of New Jersey; Piscataway; NJ; USA