Nielsen 2014.

Study characteristics
Methods	Design: RCT, parallel, 2‐centre trial. Trial authors wrote, "our study may be considered a feasibility study" (Nielsen 2014 p 8) Setting: orthopaedic departments at 1 university teaching hospital and 1 general hospital, Copenhagen, Denmark Recruitment: June 2009 to May 2011 Maximum follow‐up: 30 days
Participants	66 participants at least 18 years of age scheduled for elective hip revision surgery Liberal group: n = 33; median age (5% to 95% range) = 72 (54 to 89) years Restrictive group: n = 33; median age (5% to 95% range) = 68 (43 to 86) years
Interventions	Liberal group: received transfusion at Hb of 8.9 g/dL (5.5 mmol/L) Restrictive group: received transfusion at Hb of 7.3 g/dL (4.5 mmol/L) Target levels of Hb were > 8.9 g/dL in the liberal group and 7.3 g/dL to 8.9 g/dL in the restrictive group
Outcomes	Primary outcome: 'Timed up and go' test Other outcomes included: pneumonia, wound infection, GI complications, dizziness, hypotension, fatigue, deep vein thrombosis, falls
Notes	Trial registration (prospective): NCT00906295 Trial funding: "the first author has received an unrestricted research grant from the TrygFonden foundation, Denmark. TrygFonden has not taken any part in designing the study, analyzing the data or approving the manuscript" (Nielsen 2014 p 8) COI statement by investigators: "the authors declare that they have no competing interests" (Nielsen 2014 p 8)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	A dedicated computer program (Idefix) was used after participants' baseline data were entered. Allocation was written on a form, which was kept in the investigator's office, and allocation could be accessed only by the investigator in charge of administrating RBCs
Allocation concealment (selection bias)	Low risk	Only 1 investigator had access to the programme. Investigators at the other hospital had to call this investigator to randomise
Blinding of participants and personnel (performance bias) Objective outcomes	Low risk	Blinding of personnel for this intervention is not feasible, but in our view, for objective outcomes such as mortality (the primary outcome used within this review), we graded risk of bias as 'low' Allocation and Hb during the testing period were concealed from participants, but the investigator, staff in the operating room, and staff at the ward could not be blinded
Blinding of outcome assessment (detection bias) Objective measures	Low risk	Blinding of mortality (the primary outcome used within this review) is not relevant, and we graded risk of bias as 'low' The physiotherapist testing the participant was blinded, but it is not stated who reviewed medical records for other outcomes
Blinding of outcome assessment (detection bias) Subjective measures	Low risk	Timed up and go test, assessed by blinded physiotherapist
Incomplete outcome data (attrition bias) All outcomes	Low risk	No attrition bias was apparent, but patient flow identified losses to primary analysis (8 in restrictive arm, 5 in liberal arm)
Selective reporting (reporting bias)	Low risk	Trial was prospectively registered. All prespecified outcomes were reported. No deaths were reported in either group
Other bias	Unclear risk	Transfusion threshold was never reached in around half of recruited patients