Horstmann 2014b.

Study characteristics
Methods	Design: RCT, parallel two‐arm, multicentre study Setting: two hospitals in the Netherlands (non‐academic regional hospital, Zwolle; district hospital, Haarlem) Recruitment: February 2007 to February 2009 Maximum follow‐up: 3 months postoperatively
Participants	115 participants undergoing primary total knee arthroplasty were randomised to one of the following groups: Autologous blood transfusion (ABT) group (Cell salvage/intervention group): N = 59. Mean (SD) age 68 (9). M:F 17:42. Mean (SD) BMI 28.8 (5.1). No drainage group (Control/no cell salvage group): N = 56. Mean (SD) age 69 (8). M:F 17:39. Mean (SD) BMI 29.3 (5.2). The groups were balanced with regard to demographic and preoperative variables.
Interventions	Autologous blood re‐transfusion (ABT) group (Cell salvage/intervention group):participants in the cell salvage group received postoperative autologous blood salvage and re‐transfusion using the Bellovac Autologous Blood Transfusion drain (Astratech, Mölndal, Sweden). The drain was inserted at the end of the operative procedure and low‐suction drainage was commenced 30 minutes later. Drained blood was re‐transfused within 6 hours after surgery. No more than 1500 mL of drained blood could be re‐transfused and the drain was removed at 24 hours postoperatively. No drainage group (Control/no cell salvage group): the control group did not receive a drain.
Outcomes	Outcomes reported: intraoperative blood loss, postoperatively drained blood loss, amount of re‐transfused drained blood, allogeneic blood transfusions, incidence of haematomas, wound‐healing problems, postoperative pain, duration of hospital admission, adverse events, total blood loss
Notes	Transfusion protocol: allogeneic transfusion given according to Dutch guidelines. The transfusion trigger was 6.4 g/dL for American Society of Anesthesiologists (ASA) 1 patients, 8 g/dL for ASA 2/3 patients, and 9.6 g/dL for ASA 4 patients. Prospective registration status: the study was not prospectively registered with a trials registry. Ethical approval: the study was approved by the Institutional Medical Ethics Committee, Isala Clinics, Zwolle, the Netherlands. Language of publication: English 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	Authors do not state how the randomisation sequence was generated e.g. computer‐generated sequence
Allocation concealment (selection bias)	Low risk	Sealed, opaque envelopes used to conceal allocation
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: additional allogeneic blood transfusions were given based on the Dutch allogeneic blood transfusion guidelines. The trigger for allogeneic transfusions was an Hb level of 6.4 g/dL in patients with American Society of Anesthesiologists (ASA) physical classification 1, 8.0 g/ dl in ASA classifications 2 and 3, and 9.6 g/dL in ASA classification 4, as well as in those whose cardiac output failed to increase to compensate for dilution
Blinding of participants and personnel (performance bias) Subjective: all other outcomes	Low risk	Surgeons were blinded to allocation until the end of surgery, at which point the allocation was revealed. Participant blinding is not 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	Unclear risk	Doctors reviewing participants at follow‐up in the outpatient clinic were blinded to their treatment allocation; however, it is unclear whether outcome assessment of outcomes reported during the admission was blinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants enroled and randomised in the study are accounted for in the outcome data
Selective reporting (reporting bias)	Unclear risk	No trial registration or published protocol is available to compare
Other bias	Low risk	Authors declare no conflicts of interest. Funding source not disclosed.