Table 1.

Quality of cohort studies evaluated with modified Newcastle-Ottawa scale

Ref.	Case definition	Selection		Definition of controls	Comparability		Outcomes		Quality score
		Represen- tativeness	Selection of controls		Comparable for 1, 2, 3	Comparable for 4, 5	Assessment of outcomes	Integrity of follow-up
Choi et al[16], 2012	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	8
Choi et al[17], 2014	Yes	No	Yes	Yes	No	No	Yes	Yes	5
Makk et al[19], 2014	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	8
Marubashi et al[20], 2013	Yes	No	Yes	Yes	2, 3	4	Yes	Yes	7
Nagai et al[21], 2012	Yes	No	Yes	Yes	1, 3	4	Yes	Yes	7
Samstein et al[22], 2015	Yes	No	Yes	Yes	Yes	No	Yes	Yes	7
Soubrane et al[12], 2006	Yes	No	Yes	Yes	1,3	4	Yes	Yes	7
Suh et al[23], 2015	Yes	No	Yes	Yes	No	No	Yes	Yes	5

1 = gender; 2 = body max index; 3 = graft generation; 4 = age; 5 = haemoglobin.