[1] Stanford, Dept Med, Div Gastroenterol, Palo Alto, CA 94304 USA
[2] Vet Affairs Palo Alto Hlth Care Syst, Gastroenterol Sect, Palo Alto, CA USA
[3] Alameda Cty Publ Hlth Dept, Div Communicable Dis Control & Prevent, TB Sect, San Leandro, CA USA
[4] Yale, Dept Med, Div Digest Dis, New Haven, CT USA