Touzopoulos 2021.

Study characteristics
Methods	Design: RCT, parallel two‐arm, single‐centre study Setting: university teaching hospital, Alexandroupolis, Greece Recruitment: January 2020 to August 2020 (study dates) Maximum follow‐up: postoperative
Participants	40 participants undergoing total knee arthroplasty were randomly allocated to one of two groups: Group 1 (Self‐transfusion of collected blood) (Cell salvage/intervention group): N = 20. M:F 4:16. Mean(SD) age 68 (7.5). Mean (SD) BMI 33.6 (4.9) Group 2 (Conventional drain) (Control/no cell salvage group): N = 20. M:F 4:16. Mean (SD) age 69.8 (7.6). Mean (SD) BMI 31.1 (5.3) No significant differences between groups at baseline.
Interventions	Group 1 (Self‐transfusion of collected blood) (Cell salvage/intervention group): the transfusion filter set for salvaged blood (Summit Medical Ltd, Gloucestershire, UK) was randomly used in 20 participants postoperatively. Participants, who received autologous blood, were transfused with the collected amount of blood, only once, 6 hours postoperatively. All participants received the same pain management medication and the same physiotherapeutic protocol until they were discharged. Group 2 (Conventional drain) (Control/no cell salvage group): participants received a conventional drain and no autotransfusion was performed. All participants received the same pain management medication and the same physiotherapeutic protocol until they were discharged.
Outcomes	Outcomes reported: serum gentamicin level, total blood loss, haemoglobin concentration, renal function, wound drain fluid level, number of participants exposed to donor blood, number of units of donor blood given
Notes	Transfusion protocol: a "low transfusion trigger point (haemoglobin < 9 g/dL) was used, as a protocol in our department, since it had been proven to be safe and effective when reducing the need of allogeneic blood transfusion". Prospective registration status: the study was retrospectively registered, 8 months following study commencement. Ethical approval: the study was approved by the ethics committee of the host institution. Language of publication: English Trial funding: none reported Conflicts of interest: none reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Unclear how randomisation sequence was generated: "The randomisation process was non‐blinded and was made with the method of 'sealed envelopes' containing the sentences 'use of self‐transfusion' or 'no self‐transfusion'".
Allocation concealment (selection bias)	High risk	Envelopes sealed but not necessarily opaque. Allocation was unblinded: "The randomisation process was non‐blinded and was made with the method of 'sealed envelopes' containing the sentences 'use of self‐transfusion' or 'no self‐transfusion'".
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	Low risk	Transfusion protocol in place: "A low transfusion trigger point (haemoglobin < 9 g/dL) was used, as a protocol in our department, since it had been proven to be safe and effective when reducing the need of allogeneic blood transfusion".
Blinding of participants and personnel (performance bias) Subjective: all other outcomes	Unclear risk	Unblinded trial, no defined protocol that could prevent performance bias
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	Low risk	Unblinding of allocation may impact subjective outcomes but the outcomes of interest reported here include units transfused, number of patients exposed to allogeneic blood transfusion, and blood loss. Lack of blinding is mitigated by the use of a transfusion protocol, and authors provide calculation for total blood loss.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reported and none lost to follow up; number analysed = number randomised
Selective reporting (reporting bias)	High risk	Trial registration available (retrospectively registered): but when viewing the protocol on Clinical Trials register (NCT04505748), the only primary outcome has been defined as gentamicin serum concentration. No other outcomes of interest are listed.
Other bias	Low risk	No significant baseline imbalances. Funding (none) and conflicts (none) reported