Table 3.

Study Quality Assessment

Author	Representativeness	Ascertainment of exposure	Ascertainment: two reviewers with IRR reported	Ascertainment: criteria for preventability specifically defined	Outcome not present at start of the study	Assessment of outcome	Was follow-up long enough?	NOS
Random or consecutive cohorts
Engel,15 2007	*	*	–	*	*	*	*	6/7
Hogan,16 2012	*	*	*	*	*	*	*	7/7
Sorinola,17 2012	*	*	–	*	*	*	*	6/7
Baines,18 2015	*	*	*	*	*	*	*	7/7
Hogan,19 2015	*	*	*	*	*	*	*	7/7
Flaatten,20 2017	*	*	–	*	*	*	*	6/7
Kobewka,21 2017	*	*	*	*	*	*	*	7/7
Rogne,22 2019	*	*	–	*	*	*	*	6/7
Selected cohorts and comparable definitions of preventable
Dubois,23 1988	–	*	*	*	*	*	*	6/7
Hayward,24 2001	–	*	*	*	*	*	*	6/7
Ksouri,25 2010	–	*	–	*	*	*	*	5/7
Goulet,26 2015	–	*	*	*	*	*	*	6/7
Roberts,27 2017	–	*	–	*	*	*	*	5/7
Selected cohorts and different definitions of preventable
Best,28 1994	–	*	*	*	*	*	*	6/7
Lu,29 2006	–	*	*	–	*	*	*	5/7
Klein,30 2017	–	*	–	–	*	*	*	4/7

IRR, inter-rater reliability; NOS, Newcastle Ottawa Scale

*Asterisk indicates item achieves one point on the NOS