[1] Harvard Univ, Sch Med, Brigham & Womens Hosp, Div Pharmacoepidemiol & Pharmacoecon,Dept Med, Boston, MA 02115 USA
[2] Harvard Univ, Sch Med, Brigham & Womens Hosp, Div Renal,Dept Med, Boston, MA USA
[3] Univ Tennessee, Ctr Hlth Sci, Off Chancellor, Memphis, TN 38163 USA