[1] Univ Cologne, Inst Populat Hlth, Fac Med, Cologne, Germany
[2] Univ Cologne, Univ Hosp Cologne, Cologne, Germany
[3] Amer Univ Beirut, Dept Med, Beirut, Lebanon
[4] McMaster Univ, Dept Hlth Res Methods Evidence & Impact, Hamilton, ON, Canada
[5] Univ Cologne, Univ Hosp Cologne, Ctr Integrated Oncol Aachen Bonn Cologne Duesseldo, Fac Med,Evidence Based Med,Dept Internal Med 1, Kerpener Str 62, D-50937 Cologne, Germany
[6] Univ Hosp Wurzburg, Dept Anaesthesiol Intens Care Emergency & Pain Med, Wurzburg, Germany
[7] Cochrane Cent Execut, Editorial & Methods Dept, St Albans House,57-59 Haymarket, London SW1Y 4QX, England
[8] Amer Univ Beirut, Raf Hariri Sch Nursing, POB 11-0236, Beirut 11072020, Lebanon