[1] Permanente Med Grp, Oakland, CA USA
[2] Fred Hutchinson Canc Res Ctr, HIVNET Stat Ctr, Seattle, WA 98104 USA
[3] Univ Calif San Francisco, San Francisco, CA 94143 USA
[4] Denver Dept Publ Hlth, Denver, CO USA
[5] New York Blood Ctr, Lab Epidemiol, New York, NY 10021 USA
[6] Fenway Community Hlth Ctr, Boston, MA USA
[7] Univ Washington, Seattle, WA 98195 USA
[8] ABT Associates Inc, Cambridge, MA 02138 USA
[9] ABT Associates Inc, Bethesda, MD USA
[10] Univ Penn, Philadelphia, PA 19104 USA
[11] Philadelphia Vet Affairs Med Ctr, Philadelphia, PA USA
[12] NYU, Med Ctr, New York, NY 10016 USA
[13] Boston Univ, Sch Publ Hlth, Boston, MA USA
[14] San Francisco Dept Publ Hlth, San Francisco, CA 94102 USA