1. Department of Medicine, Division of Gastroenterology and Hepatology, University of California—San Francisco, San Francisco, California, USA
2. School of Medicine Technology Services, University of California—San Francisco, San Francisco, California, USA
3. Family Health Centers, NYU-Langone Medical Center, Brooklyn, New York, USA
4. Department of Epidemiology and Biostatistics, University of California—San Francisco, San Francisco, California, USA