Methods	A prospective, randomised controlled study was conducted to analyse the effect of postoperative autotransfusion on the need for allogeneic transfusion and to determine the quality of post-operatively collected drainage blood and to compare it with other blood sources in patients undergoing primary total hip replacement. Method of randomisation and allocation concealment were not described
Participants	60 patients undergoing primary total hip replacement were randomly allocated to one of two groups: Group 1 (Autotransfusion group): n=30; M//F=14//16; mean (sd) age = 68 (12) years Group 2 (Control group): n=30; M//F=12//18; mean (sd) age = 71 (11) years
Interventions	Group 1: Autotransfusion group had their shed blood processed by the BIODREN system. This system is a closed autologous blood recovery system. The vacuum pump provides an adjustable constant vacuum kept below 100mmHg. The system is connected to two CH14 drains during the final stage of the operation and active suction is initiated after skin closure. When collection of shed blood in the reservoir is completed (600mls of blood is collected or after maximum of 360 minutes of collection is passed) the blood flows through a 260 micron filter to the blood bag, from which autotransfusion through a 40 micron filter (Pall blood transfusion set) is done. Group 2: Control group did not receive autotransfusion.
Outcomes	Outcomes reported: number of patients transfused allogeneic blood, amount of allogeneic blood transfused, blood loss, haematological variables
Notes	Transfusion threshold: patients received allogeneic blood to maintain a haemoglobin level of 10.0g/dL or haematocrit level of 30%
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