Jensen 1996.

Methods	Design: Parallel group RCT Country: Denmark Multicentre study: Yes (2 university departments of colorectal surgery; page 844). Setting: Hospital Follow‐up: 30 days after surgery Unit of allocation: Patients Unit of analysis: Patients
Participants	Inclusion criteria: Patients admitted for elective colorectal surgery Exclusion criteria: < 18 years of age, need for emergency surgery, or immunosuppressive treatment, except steroids Patients enrolled: 589 Patients randomised: 589 Leucocyte‐depleted red cells group: 290 Buffy‐coat‐poor red cells group: 299 Patients transfused: 260 Patients considered for the analysis: 586 Main characteristics of patients: Age = Median (range): Leucocyte‐depleted red cells group = 69 (35 to 89) years; Buffy‐coat‐poor red cells group = 68 (29 to 92) years Percentage of men: Leucocyte‐depleted red cells group = 50%; buffy‐coat‐poor red cells group = 48% Number of procedures: Sigmoid resection: Leucocyte‐depleted red cells group = 11; Buffy‐coat‐poor red cells group = 19 Blood loss = Median (range): Leucocyte‐depleted red cells group = 715 (50 to 3500) mL; Buffy‐coat‐poor red cells group = 805 (10 to 4300) mL.
Interventions	Leucocyte‐depleted red cells group (the timing of leukoreduction is not reported). Buffy‐coat‐poor red cells group. Cointervention: Quote: "All patients received an intravenous dose of cefuroxime 3 g and metronidazole 1.5 g after induction of anaesthesia" (Page 842).
Outcomes	This RCT did not specify by primary or secondary outcomes. Abdominal wound infection: Accumulation of pus with spontaneous discharge or requiring surgical drainage. Deep surgical infection: Intraabdominal abscess or septicaemia. Pneumonia: Fever and infiltrate on chest radiography. Surgical complications: Anastomotic leakage, abdominal wound dehiscence, intra‐abdominal bleeding and ileus. Operation‐related mortality: Death during hospital stay or within 30 days after surgery.
Notes	Trial Registration: Not reported. Funding: Not reported. Role of sponsor: Not stated. A priori sample size estimation: Yes. Conducted: Between January 1992 and January 1995. Declared conflicts of interest: Not reported.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "were randomly allocated using sealed envelopes to receive either..." (Page 841). Comment: Insufficient information to permit judgement of ‘low risk’ or ‘high risk’.
Allocation concealment (selection bias)	Unclear risk	Quote: "were randomly allocated using sealed envelopes to receive either..." (Page 841) Use of opaque envelopes is not reported.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Comment: Insufficient information to permit judgement of ‘low risk’ or ‘high risk’.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "Physicians who were blinded to the transfusion protocol performed follow‐up examinations..." (Page 842).
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: All patients transfused were analysed. (Page 842).
Selective reporting (reporting bias)	Low risk	Comment: The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified.
Other bias	Unclear risk	Comment: Sample size estimation took into account loss to follow‐up due to no transfusion.