Methods	Consecutive patients undergoing elective knee arthroplasty at two institutions were enrolled in the study. Method of randomisation and allocation concealment was not described
Participants	81 patients undergoing elective knee arthroplasty were randomly assigned to one of two groups: Group 1 (Autotransfusion group): n=39; M//F=14//25; mean (sd) age = 69.3 (6.9) years Group 2 (Control group): n=40; M//F=14//26; mean (sd) age = 71.0 (9.0) years
Interventions	Group 1: Autotransfusion group underwent drainage and autotransfusion transfusion using a Solcotrans system. The autologous blood collected into the drainage and transfusion device was transfused if specific transfusion guidelines were met. Patients were transfused the initial unit of Solcotrans blood if 350ml or more had been collected within 3 hours of the patients entry to the recovery room. The 3-hour collection time provided for collection and transfusion of the blood within the maximum interval of 6 hours. After successful collection and transfusion of the first autologous blood unit, a second autologous blood collection device was attached. For this and subsequent collections, autologous blood was transfused if 150ml or more was collected within 3 hours. When the rate of drainage was less than 250ml of blood within a 3 hour period, a subsequent drainage and transfusion device was not attached. The first Solcotrans device attached to the drain contained 40ml of ACD-A. Group 2: Control group had their drained blood collected by a Davol suction unit and discarded. The Davol unit was the current standard practice in the two study centres. Patients assigned to the Davol suction group received 1 unit of allogeneic red cells if more than 500ml of blood drained from the surgical site within a 2 hour period. Subsequently, whenever drainage exceeded 500ml within a 2 hour period, 1 unit of allogeneic blood was transfused.
Outcomes	Outcomes reported: amount of allogeneic blood transfused, number of patients transfused allogeneic blood, adverse events, blood loss, coagulation variables, venogram tests
Notes	Transfusion thresholds: on postoperative Day 2 through to Day 5, the criteria for allogeneic red cell transfusions were identical for both groups. Patients were given one unit of red cell concentrate if their haemoglobin was within the range of 8.0 to 8.9g/dL, two units when the value was from 7.0 to 7.9g/dL, three units when the value was from 6.0 to 6.9g/dL, and four units if the value was from 5.0 to 5.9g/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)	Unclear risk	Method used to conceal treatment allocation was unclear.
Blinding (performance bias and detection bias) All outcomes	High risk