[1] Baylor Coll Med, Dept Internal Med, Gastroenterol & Hepatol Sect, Houston, TX 77030 USA
[2] Texas Tech Univ Hlth Sci Ctr, Paul L Foster Sch Med, Dept Internal Med, Div Gastroenterol, El Paso, TX USA
[3] Texas Tech Univ Hlth Sci Ctr, Paul L Foster Sch Med, Dept Biomed Sci, Div Biostat & Epidemiol, El Paso, TX USA