Methods	Between May 2005 and December 2005, 178 patients were entered into the study. All patients over 55 years with osteoarthritis and/or inflammatory arthritis of the knee, and awaiting total knee replacement (TKR), were considered for the study. In a pre-assessment clinic patients were randomly assigned into two groups by sealed envelopes
Participants	178 patients undergoing total knee replacement were randomised to one of two groups: Group 1 (Autologous retransfusion group): n=92, M//F=43//49, mean (range) age = 70.3 (55.2-88.5) years Group 2 (Control group): n=86, M//F=39//47, mean (range) age = 70.4 (57.9-87. 1) years
Interventions	Group 1: Autologous retransfusion group (Bellovac ABT autotransfusion sytem) had the blood collection suction bellows connected to an autologous transfusion bag with a 200mm filter and a one-way valve. The transfusion bag was connected to a transfusion set with a 40um filter. The drain was opened 20 minutes after tourniquet release. The shed blood was returned to the patient after collecting up to 500mls and no later than 6 hours after surgery. A maximum of 1200mls was re-transfused. Group 2: Control group (standard vacuum drain) had blood collected in the vacuum drains discarded.
Outcomes	Outcomes reported: number of patients transfused allogeneic blood, hospital length of stay, adverse events
Notes	Transfusion threshold: allogeneic blood transfusion was given if the haemoglobin level was less than 8.0g/dL
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)	High risk	Sealed envelopes were used to conceal treatment allocation.
Blinding (performance bias and detection bias) All outcomes	High risk