Nemani 2019.

Study characteristics
Methods	Design: RCT, parallel two‐arm, single‐centre study Setting: speciality hospital, New York, NY, USA Recruitment: recruitment and study dates not reported Maximum follow‐up: 3 months postoperatively
Participants	63 participants undergoing long posterior spinal fusion for deformity were randomised to one of two groups: Group 1 (OrthoPAT) (Cell salvage/intervention group): N = 30. Mean (SD) age 50.5 (17). M:F 5:25 Group 2 (Constavac) (Control/no cell salvage group): N = 33. Mean (SD) age 51.5 (17.6). M:F 10:23 There were no‐between group differences at baseline.
Interventions	Group 1 (OrthoPAT) (Cell salvage/intervention group): the cell salvage group (autotransfusion group) received the OrthoPAT cell salvage and reinfusion system. The reinfusion drain was converted to a standard (Constavac) drain when the output was < 50 mL/4 hours. The drain was removed when output was < 50 mL/8 hours. Group 2 (Constavac) (Control/no cell salvage group):the standard drain (control) group received a standard subfascial closed suction drain (Constavac, Stryker). The drain was removed when output was < 50 mL/8 hours.
Outcomes	Outcomes reported: postoperative homologous blood transfusion volume, 24‐hour drain output postoperatively, total drain output, transfusion‐related reactions and complications
Notes	Transfusion protocol: participants received either homologous or autologous blood postoperatively when Hb < 8 g/dL or they had symptomatic anaemia, including sustained hypotension, (SBP < 90 mmHg for two consecutive measurements), sustained tachycardia (heart rate > 110 bpm for two consecutive measurements), dizziness, fatigue, orthostasis as assessed by attending anaesthesiologist or internist. Prospective registration status: the study was not prospectively registered with a trials registry. Ethical approval: the study was approved by the Institutional Review Board for Hospital for Special Surgery, New York, USA. 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)	Low risk	Randomisation was performed by a circulating nurse opening the randomisation envelope. Allocation was performed by the Epidemiology and Biostatisitcs Core using randomisation software on a 1:1 basis preoperatively. Participants were assigned to a drain type depending on the order in which they were enroled based on the pre‐determined randomisation order. A block randomisation scheme was used.
Allocation concealment (selection bias)	Low risk	Allocation was performed by the Epidemiology and Biostatisitcs Core located elsewhere and investigators were blinded to the block size of the block randomisation protocol used.
Blinding of participants and personnel (performance bias) Objective outcome: mortality	Low risk	Objective outcome (mortality) unlikely to be influenced by blinding
Blinding of participants and personnel (performance bias) Subjective: transfusion protocol	Low risk	Transfusion protocol in place: participants received either homologous or autologous blood postoperatively when Hb < 8 g/dL or they had symptomatic anaemia, including sustained hypotension, (SBP < 90 mmHg for two consecutive measurements), sustained tachycardia (heart rate > 110 bpm for two consecutive measurements), dizziness, fatigue, orthostasis, as assessed by attending anaesthesiologist or internist.
Blinding of participants and personnel (performance bias) Subjective: all other outcomes	Unclear risk	No mention of blinding, use of drains may have masked allocation. Many outcomes not clearly defined, so may be affected by lack of blinding
Blinding of outcome assessment (detection bias) Objective outcomes: mortality and transfusions	Low risk	Objective outcome (mortality) unlikely to be influenced by blinding
Blinding of outcome assessment (detection bias) Subjective outcomes	Unclear risk	No mention of blinding, use of drains may have masked allocation. Many outcomes not clearly defined, so may be affected by lack of blinding
Incomplete outcome data (attrition bias) All outcomes	Low risk	Two participants were lost to follow‐up in Group 1, which is unlikely to have had a significant impact on the effect demonstrated.
Selective reporting (reporting bias)	Unclear risk	No trial registration or published protocol is available to compare, and vague description of secondary outcome measures (additional data collected included various patient demographic and anthropomorphic variables, and other preoperative, intraoperative, and postoperative data.)
Other bias	Low risk	Funding and conflicts of interest reported. No identified baseline imbalance