Kristensen 1992.

Study characteristics
Methods	Design: RCT, parallel two‐arm, single‐centre study Setting: regional hospital, Vejle, Denmark Recruitment: recruitment and study dates not reported Maximum follow‐up: 4 days postoperatively
Participants	56 participants undergoing total hip or knee arthroplasty were randomised into 2 groups, with subgrouped data available for hip and knee surgery patients for some information: Autologous hip (Cell salvage/intervention group): N = 18. Mean (range) age: 68 (18 to 84). Autologous knee (Cell salvage/intervention group): N = 13. Mean (range) age: 65 (6 to 86) Homologous hip (Control/no cell salvage group): N = 16. Mean (range) age: 66 (50 to 81) Homologous knee (Control/no cell salvage group): N = 9. Mean (range) age: 71 (61 to 81) Groups were similar with regard to baseline characteristics, although few details were provided.
Interventions	Autologous group (Cell salvage/intervention group): Solcotrans Orthopaedic drainage system was used to collect blood postoperatively. Reinfusion was performed either when the drainage bag was full, or after 6 hours of collection time if a minimum of 300 mL of blood was present in the drainage bag. Homologous blood was given if required. Homologous group (Control/no cell salvage group): drainage blood discarded instead of retransfused.
Outcomes	Outcomes reported: Homologous blood requirement, blood loss
Notes	Transfusion protocol: The criterion for giving homologous blood transfusion was clinical judgement, taking into account the haemodiluting effect of parenteral solutions given intraoperatively to maintain normovolaemia. The critical haemoglobin level for administering homologous blood was 8.5 g/dL. Prospective registration status: the study was published prior to 2010. Ethical approval: it is not clear whether the study was approved by an ethics committee or institutional review board. Language of publication: English Study groups: for the purpose of our review, we have included the autologous hip and autologous knee groups as the cell salvage/intervention group. Homologous hip and homologous knee groups have been included as the control/no cell salvage group. Trial funding: not reported Conflicts of interest: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Methods poorly described
Allocation concealment (selection bias)	Unclear risk	Methods poorly described
Blinding of participants and personnel (performance bias) Objective outcome: mortality	Low risk	No objective outcomes reported (mortality unlikely to be affected by blinding if reported in future publications)
Blinding of participants and personnel (performance bias) Subjective: transfusion protocol	High risk	Transfusion protocol given. Although it does also state 'clinical judgement', risk of deviation from protocol as 8.5 g/dL is 'critical' transfusion threshold, so patients may receive transfusions at Hb above this. Quote: "The criterion for giving homologous blood transfusion was clinical judgement, taking into account the haemodiluting effect of parenteral solutions given intraoperatively to maintain normovolemia. The critical hemoglobin level for administering homologous blood was 8.5 g/dL".
Blinding of participants and personnel (performance bias) Subjective: all other outcomes	High risk	Unclear if blinded but unlikely, and volume of blood loss measurement poorly described
Blinding of outcome assessment (detection bias) Objective outcomes: mortality and transfusions	Low risk	No objective outcomes reported (mortality unlikely to be affected by blinding if reported in future publications)
Blinding of outcome assessment (detection bias) Subjective outcomes	High risk	Unclear if blinded but unlikely, and volume of blood loss measurement poorly described
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear if number analysed = number randomised.
Selective reporting (reporting bias)	Unclear risk	No trial registration or published protocol is available to compare
Other bias	Unclear risk	Lack of baseline characteristics provided – only age and operation (hip or knee). No conflict of interest statement provided