Gu 1996.

Study characteristics
Methods	Prospective, randomised study Accepted for publication: 21 December 1995 Number of study centres and locations: single centre; Departments of Cardiothoracic Surgery University Hospital, Groningen, the Netherlands
Participants	Thirty patients undergoing elective heart operations were randomly allocated to a leucocyte‐depletion group (n = 20) or a control group (n = 10). Mean age: 60.67 years Sex (female/male ratio): 26.67% No high‐risk patients Inclusion criteria: not specified Exclusion criteria: allergy or recurrent infection, reoperation, and emergency operation
Interventions	Intervention group: all residual blood was filtered by leucocyte removal filters and re‐infused after CPB. Control group: an identical amount of residual blood after CPB was re‐infused without filtration.
Outcomes	Leucocyte depletion (leucocyte and granulocyte counts, Plt levels), lung function (partial arterial oxygen tension, PAP, PCWP, PVR), other clinical parameters (duration of postoperative intubation, blood loss, ICU LOS and hospital LOS, infections), laboratory parameters, and inflammatory mediators (thromboxane B2, IL‐6, and IL‐2) Blood samples were taken at the baseline before operation, at the end of CPB before transfusion of the leucocyte‐depleted blood, at the end of operation during skin closure, 1 hour and 3 hours after the patient's arrival in the ICU, and at 6 a.m. the next day in the ICU.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	There were no significant differences between the leucocyte‐depletion group and the control group. No randomisation method description is given.
Allocation concealment (selection bias)	Unclear risk	No allocation information
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not specified; unlikely for personnel because of the nature of the intervention
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not specified
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants completed the study (uneventful in the two groups); no trial group changes, no withdrawals, and no losses to follow‐up were reported, but no ITT analysis. Data from all the participants were included in the final analysis.
Selective reporting (reporting bias)	Unclear risk	IL‐2 was not detectable in any of the samples (but this could be in agreement with other cardiac surgery studies). The other outcomes were reported properly.
Other bias	Low risk	No funding was disclosed.