[1] Univ Ioannina, Sch Med, Dept Hyg & Epidemiol, Clin & Mol Epidemiol Unit, GR-45110 Ioannina, Greece
[2] Univ Ioannina, Sch Med, Dept Hyg & Epidemiol, Clin Trials & Evidencebased Med Unit, GR-45110 Ioannina, Greece
[3] Fdn Res & Technol, Biomed Res Inst, Ioannina, Greece
[4] Tufts Med Ctr, Inst Clin Res & Hlth Policy Studies, Dept Med, Boston, MA USA