Dutton 2012.

Study characteristics
Methods	Design: RCT, parallel two‐arm, single‐centre feasibility study Setting: university teaching hospital, Coventry, Warwickshire, UK Recruitment: January 2009 to July 2009 Maximum follow‐up: 48 hours postoperatively
Participants	48 participants scheduled for elective total knee replacement were randomised to one of two treatment arms: Retransfusion drain group (Cell salvage/intervention group)N = 23. Mean (range) age 68.7 (56 to 84). M:F 10:13. No drain group (Control/no cell salvage group): N = 25. Mean (range) age 70.5 (56 to 95). M:F 10:15. The study does not report whether there were any differences between groups at baseline.
Interventions	Retransfusion drain group (Cell salvage/intervention group): participants in the retransfusion drain group received a Bellovac Autologous Blood Transfusion ((ABT) Astra Tech, Molndal, Sweden) drain at the time of wound closure. The drain collects blood from the operative site postoperatively. Salvaged blood is transferred to a transfusion bag via a 200 mm filter prior to retransfusion. Drains were opened 20 minutes after tourniquet release and allowed to drain for 6 hours. Salvaged blood was retransfused if > 80 mL was collected. Drains were removed after 6 hours. No drain group (Control/no cell salvage group): participants in the control group did not receive a drain.
Outcomes	Outcomes reported: postoperative haemoglobin concentration at 48 hours, complications and adverse events, number of participants requiring allogeneic transfusion, number of allogeneic units transfused
Notes	Transfusion protocol: a transfusion threshold was not used. The decision to transfuse allogenic blood was left to the independent clinical teams as per their normal practice. Prospective registration status: the study was not prospectively registered on a trials registry. The study was performed as a pilot study, for which registration is not required. Ethical approval: the study was approved by the local research ethics committee for University Hospitals Coventry and Warwickshire. Language of publication: English Trial funding: not reported Conflicts of interest: no competing interests declared
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants were randomised to the Retransfusion Drain or No Drain groups by means of a computer‐generated random sequence generated prior to commencement of the study
Allocation concealment (selection bias)	Low risk	Sequentially‐numbered, sealed, opaque envelopes used during the randomisation process and allocation to study arm was only revealed at the point in the operation at which a drain would be inserted.
Blinding of participants and personnel (performance bias) Objective outcome: mortality	Low risk	Objective outcome (mortality) unlikely to be influenced by blinding.
Blinding of participants and personnel (performance bias) Subjective: transfusion protocol	High risk	No transfusion protocol in place: decision to transfuse allogenic blood was left to the independent clinical teams as per their normal practice.
Blinding of participants and personnel (performance bias) Subjective: all other outcomes	High risk	Each surgeon followed their normal clinical practice and were unblinded to group allocation
Blinding of outcome assessment (detection bias) Objective outcomes: mortality and transfusions	Low risk	Objective outcome (mortality) unlikely to be influenced by blinding
Blinding of outcome assessment (detection bias) Subjective outcomes	High risk	Each surgeon followed their normal clinical practice and were unblinded to group allocation; no other statement regarding outcome assessors
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants recruited to the study and randomised were accounted for at follow‐up and within the outcomes reported, no apparent loss to follow‐up, but no breakdown presented
Selective reporting (reporting bias)	Unclear risk	No trial registration or published protocol is available to compare
Other bias	High risk	Significant protocol deviations with regard to re‐transfusion of blood. Raises suspicion of trial conduct. Declared no competing interests