1 Center for Innovations in Quality, Effectiveness and Safety, Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA.
2 Section of Health Services Research, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA.
3 Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine and Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA.
4 Department of Biostatistics, University of Texas MD Anderson Cancer Center, Houston, Texas, USA.