RT Journal Article SR Electronic T1 Confounding explains ‘deaths avoided’ JF BMJ Quality & Safety JO BMJ Qual Saf FD BMJ Publishing Group Ltd SP 175 OP 175 DO 10.1136/bmjqs-2014-003748 VO 24 IS 2 A1 Johan Michael van Schalkwyk YR 2015 UL http://qualitysafety.bmj.com/content/24/2/175.1.abstract AB