Ritter 1994.

Methods	A randomised, prospective study of patients undergoing primary total hip or total knee replacement over a six‐month period. Method of randomisation and allocation concealment were not described.
Participants	415 patients undergoing primary total hip or total knee replacement were randomly allocated to one of two groups: Group 1 (Autotransfusion group): n=215 Group 2 (Control group): n=200 NB: Demographic data were not reported.
Interventions	Group 1: Autotransfusion group received unwashed, filtered autologous blood processed by the Solcotrans autotransfusion system. Group 2: Control group had no drainage system.
Outcomes	Outcomes reported: number of patients transfused allogeneic blood, amount of transfused blood, adverse events, knee flexion.
Notes	Transfusion threshold: allogeneic blood was transfused if the haemoglobin level fell below 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