CLINICAL & BASIC RESEARCH SQU Med J, May 2011, Vol. 11, Iss. 2, pp. 244-251, Epub. 15th May 11 Submitted 24th Aug 10 Revision ReQ. 27th Sept & 14th Dec 10, Revision recd. 24th Oct & 22nd Dec 10 Accepted 23rd Feb 11 1Department of Medical Statistics & Epidemiology, Hamad General Hospital, Hamad Medical Corporation, Doha, Qatar; 2Evidence for Population Health Unit, School of Epidemiology & Health Sciences, University of Manchester, Manchester, U.K.; 3Hamad Trauma Center, Hamad Medical Corporation, Doha, Qatar; 4Accident and Emergency Department, Hamad Medical Corporation, Doha, Qatar. *Corresponding Author email: abener@hmc.org.qa ΩÁœä÷]<ÌrÈjfi<ÌfŒÜ÷]Ê<å_Ü÷]