1. Veterans Affairs Maryland Healthcare System, Baltimore VA Medical Center, Baltimore, MD, USA
2. Department of Medicine, Division of Gastroenterology and Hepatology, University of Maryland School of Medicine, Baltimore, MD, USA
3. Department of Pathology, University of Maryland School of Medicine, Baltimore, MD, USA
4. Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD, USA
5. Marlene and Stewart Greenebaum Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA