[1] Duke Univ, Durham, NC 27706 USA
[2] Durham VA Med Ctr, GRECC, Durham, NC USA
[3] Merck Res Labs, West Point, PA USA
[4] Harvard Vanguard Med Associates, Chelmsford, Essex, England
[5] Harvard Pilgrim Hlth Care, Dept Ambulatory Care & Prevent, Boston, MA USA
[6] Harvard Univ, Sch Med, Boston, MA USA
[7] Univ Colorado, Hlth Sci Ctr, Denver, CO USA
[8] VA Cooperat Studies Program Coordinating Ctr, West Haven, CT USA
[9] Univ Calif San Diego, La Jolla, CA 92093 USA
[10] San Diego VA Med Ctr, La Jolla, CA USA