(a).

Author	Year	Ottawa-Newcastle score	N = total	N = transfused patients	N = nontransfused patients	Hazard ratio	95% CI for HR
Kluth et al. [9]	2014	8.00	2895	1128	1767	1.1	0.99–1.22
Linder et al. [20]	2013	9.00	2060	1279	781	1.27	1.12–1.45
Moschini et al. [17]	2015	7.00	1373	463	910	1.45	1.02–2.08
Morgan et al. [21]	2013	7.00	777	323	454	1.17	1.01–1.36
Abel et al. [10]	2014	7.00	281	162	119	1.49	1.00–2.25
Abel et al. [10]	2014	7.00	1485	815	670	1.4	1.2–1.62
Soubra et al. [18]	2015	8.00	5462	1139	4323	1.109	1.011–1.21
Sadeghi et al. [22]	2012	7.00	638	209	429	1.15	0.91–1.45
Gierth et al. [23]	2015	7.00	684	423	261	1.822	1.45–2.29