Methods	Patients undergoing bi- or tri-compartmental total knee arthroplasties with a diagnosis of primary osteoarthritis were included in the study
Participants	32 patients undergoing total knee arthroplasty were randomised to one of two groups: Group 1 (Autotranfusion group): n=16, M//F=0//16, mean (sd) age = 66.9 (9.1) years Group 2 (Control group): n=2/14, M//F=2//14, mean (sd) age = 66.2 (7.1) years
Interventions	Group 1: Autotransfusion group (ConstaVac CBCII autotransfusion system) had wound drainged connected at the end of the operation. The drain fluid was collected during the first 6 hours. Collected blood was transfused at the end of the 6th hour. Reinfusion was performed using a standard 40um blood filter between the collection bag and the intravenous site. After the 6 hours any blood collected from the reinfusion drain was discarded. Group 2: Control group received standard care without autotransfusion.
Outcomes	Outcomes reported: number of patients transfused allogeneic blood, blood loss, hospital length of stay, adverse events
Notes	Transfusion threshold: allogeneic blood transfusion was given if the haemoglobin level was less than 9.0g/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)	Unclear risk	Method used to conceal treatment allocation was not described
Blinding (performance bias and detection bias) All outcomes	High risk