Topley 1956.

Study characteristics
Methods	Design: RCT, parallel 2‐arm, single‐centre trial Setting: an 'accident hospital', Birmingham, UK Recruitment: not reported. Pre‐1957 Maximum follow‐up: 3 months
Participants	22 trauma participants randomly allocated to 1 of 2 groups Liberal group: n = 10 Restrictive group: n = 12 NB: no demographic data were reported
Interventions	Liberal group: aim was to achieve 100% or more of [normal] RBC volume at the end of resuscitation Restrictive group: an attempt was made to leave RBC volume at the end of resuscitation at 70% to 80% of normal
Outcomes	Blood usage (units), blood loss, wound healing, elevated temperature, number of participants transfused, Hb. Deaths were reported, but timing and transfusion strategy were not provided
Notes	Trial registration: none ascertainable Trial funding: none reported COI statement by investigators: none reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Use of random sequence generation was not described
Allocation concealment (selection bias)	Unclear risk	Trial used sealed envelopes. When participants were considered eligible for the trial, they were placed in a severity grade and an envelope was opened to decide which transfusion schedule was to be used
Blinding of participants and personnel (performance bias) Objective outcomes	Low risk	Blinding of personnel for this intervention is not feasible, but in our view, for objective outcomes such as mortality (the primary outcome used within this review), we graded risk of bias as 'low'
Blinding of outcome assessment (detection bias) Objective measures	Low risk	Blinding of mortality (the primary outcome used within this review) is not relevant, and we graded risk of bias as 'low'
Blinding of outcome assessment (detection bias) Subjective measures	Low risk	No data from subjective outcomes (e.g. function)
Incomplete outcome data (attrition bias) All outcomes	High risk	Trial did not report in which group the deaths occurred; therefore we classified this as high risk of bias
Selective reporting (reporting bias)	High risk	Trial did not report in which group the deaths occurred; therefore we classified this as high risk of bias
Other bias	Low risk	No other biases were apparent