Amin 2008.

Study characteristics
Methods	Design: RCT, parallel two‐arm, single‐centre study Setting: District General Hospital, Colchester, Essex, UK Recruitment: May 2005 to December 2005 Maximum follow‐up: duration of hospital stay
Participants	178 participants undergoing total knee replacement were randomised to one of two groups: Autologous retransfusion drain group (Cell salvage/intervention group): N = 92. M:F 43:49. Mean (range) age 70.3 (55.2 to 88.5) Standard vacuum drain group (Control/no cell salvage group): N = 86, M:F 39:47. Mean (range) age 70.4 (57.9 to 87.1) No formal test of baseline imbalance was performed to compare the groups and the authors do not comment on whether they were similar.
Interventions	Autologous retransfusion drain group: cell salvage group (Bellovac ABT autotransfusion sytem) had the blood collection suction bellows connected to an autologous transfusion bag with a 200 mm filter and a one‐way valve. The transfusion bag was connected to a transfusion set with a 40 µm filter. The drain was opened 20 minutes after tourniquet release. The shed blood was returned to the participant after collecting up to 500 mL and no later than 6 hours after surgery. A maximum of 1200 mL was re‐transfused. Standard vacuum drain group: control group (standard vacuum drain) had blood collected in the vacuum drains discarded.
Outcomes	Outcomes reported: number of participants transfused allogeneic blood, hospital length of stay, adverse events
Notes	Transfusion protocol: allogeneic blood was transfused if the haemoglobin level fell below 80 g/L, or if the participant developed clinical signs of anaemia, such as tachycardia and postural hypotension, in the presence of a haemoglobin level of 80 g/L to 100 g/L. Prospective registration status: the study was published prior to 2010. Ethical approval: the study was approved by the local ethics committee. Language of publication: English Trial funding: not reported Conflicts of interest: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method used to generate allocation sequences was not described.
Allocation concealment (selection bias)	Unclear risk	Sealed envelopes were used to conceal treatment allocation, but doesn't mention if they were opaque.
Blinding of participants and personnel (performance bias) Objective outcome: mortality	Low risk	No objective outcomes reported (mortality unlikely to be affected by blinding if reported in future publications)
Blinding of participants and personnel (performance bias) Subjective: transfusion protocol	Low risk	Transfusion protocol in place: allogenic blood was transfused if the haemoglobin level fell below 8 g/dL, or if the participant developed clinical signs of anaemia, such as tachycardia and postural hypotension, in the presence of a haemoglobin level of 8 g/dL to 10 g/dL.
Blinding of participants and personnel (performance bias) Subjective: all other outcomes	Unclear risk	No mention of blinding of participants or personnel
Blinding of outcome assessment (detection bias) Objective outcomes: mortality and transfusions	Low risk	No objective outcomes reported (mortality unlikely to be affected by blinding if reported in future publications)
Blinding of outcome assessment (detection bias) Subjective outcomes	Unclear risk	No mention of blinding in manuscript
Incomplete outcome data (attrition bias) All outcomes	Low risk	Unclear patient flow; however, results state they analysed ITT
Selective reporting (reporting bias)	Unclear risk	No trial registration or published protocol is available to compare
Other bias	Unclear risk	No mention of funding or conflicts