Study	Reason for exclusion
Bowden 1995	The study population received other blood components along with or different from PRBC transfusion.
Bracey 2002	Non‐randomised clinical trial.
Connery 2005	Study protocol included patients with no indication of RBCs. Intervention poorly specified.
de Vries 2003	No control group.
de Vries 2004	No transfusion intervention.
Dzik 2002	Study protocol included patients with no indication of RBCs.
Efstathiou 2003	Autologous transfusion as intervention.
Gilbert 1989	The study population received other blood components along with or different from PRBC transfusion.
Gu 1996	The study population received other blood components along with or different from PRBC transfusion.
Gu 2009	Autologous transfusion as intervention.
Hayashi 2000	Autologous transfusion as intervention.
Houbiers 1994	Study protocol included patients with no indication of RBCs.
Jensen 1992	The study population received other blood components along with or different from PRBC transfusion.
Kao 1995	The study population received other blood components along with or different from PRBC transfusion (platelets intervention).
Koskenkari 2005	No transfusion intervention.
Leal‐Noval 2005	No transfusion intervention.
Llewelyn 2004	Non‐randomised clinical trial.
Nielsen 1999	Study protocol included patients with no indication of RBCs.
Opelz 1997	Control group did not receive transfusion.
Salamonsen 2005	No transfusion intervention.
Skånberg 2007	Non‐randomised clinical trial.
So‐Osman 2010	Did not report a control group.
Vamvakas 2007	Meta‐analysis.
van de Watering 2004	Narrative review.