[1] VA Palo Alto Health Care System, Palo Alto, CA
[2] Section on Medical Informatics, Department of Medicine, Stanford University, Stanford, CA
[3] Dept. of Eng.-Economic Systems, Stanford University, Stanford, CA
[4] Lab. for Medical Decision Sciences, Division of General Medical Sciences, Washington University, St. Louis, MO
[5] Section of General Medicine, VA Palo Alto Health Care System, Palo Alto, CA 94304