RT Journal Article SR Electronic T1 Correction JF Emergency Medicine Journal JO Emerg Med J FD BMJ Publishing Group Ltd and the British Association for Accident & Emergency Medicine SP 171 OP 171 DO 10.1136/emermed-2011-201045.4corr1 VO 30 IS 2 YR 2013 UL http://emj.bmj.com/content/30/2/171.abstract AB