[1] Boston Univ, Pulm Ctr, Chobanian & Avedisian Sch Med, 72 East Concord St,R-304, Boston, MA 02118 USA
[2] Boston Univ, Chobanian & Avedisian Sch Med, Sect Cardiovasc Med, Boston, MA USA
[3] Boston Univ, Chobanian & Avedisian Sch Med, Sect Rheumatol, Boston, MA USA
[4] VA Boston Healthcare Syst, Ctr Healthcare Org & Implementat Res, Boston, MA USA
[5] Boston Univ, Sch Publ Hlth, Dept Biostat, Boston, MA USA