| Study | Reason for exclusion |
|---|---|
| Atilla 2017 | RCT. Ineligible intervention (haemoglobin content‐based vs standard (unit‐based) transfusion policy, rather than threshold)) |
| Baron‐Stefaniak 2019 | RCT. Ineligible intervention; not haemoglobin threshold |
| Cholette 2017 | RCT. Ineligible participants (infants (cardiac)) |
| de Bruin 2019 | Ineligible design. Survey amongst ICU physicians reviewing transfusion practices |
| Elshinawy 2020 | RCT. Ineligible intervention; not haemoglobin threshold |
| Fogagnolo 2020 | Ineligible design. Prospective observational study |
| Fortune 1987 | RCT (reported only in an abstract) appeared to measure only oxygen utilisation. Investigators planned no clinical outcomes of interest |
| Franz 2020 | RCT. Ineligible participants (neonates (low birth weight)) |
| Haensig 2019 | RCT. Ineligible intervention (not red cell transfusion but thrombelastometry guided blood‐component therapy) |
| Hamm 2020 | RCT. Ineligible intervention (trial assessed effects of single‐unit vs multiple‐unit transfusion, rather than threshold) |
| Jain 2019 | RCT. Ineligible intervention (trial assessed effects of known haemoglobin content of packed red blood cell units vs standard transfusion practice in thalassaemia major) |
| Kirpalani 2020 | RCT. Ineligible participants: neonates |
| Koster 2016 | Ineligible design. Ineligible intervention. This single‐centred retrospective cohort study looked at coronary artery bypass patients who received either 1 to 2 or no units of blood |
| Kumar 2019 | RCT. Ineligible intervention (not red cell transfusion but thrombelastometry guided blood‐component therapy) |
| Leal‐Noval 2017 | RCT. Ineligible intervention (trial assessed effects of using a transcranial oxygen saturation threshold, as measured by near‐infrared spectroscopy, in neurocritically ill patients) |
| Osawa 2016 | RCT. Ineligible intervention (trial assessed effects of cardiac output‐guided haemodynamic therapy algorithm (goal‐directed therapy group) or usual care) |
| Robertson 2014 | RCT. Ineligible intervention/comparator. The trial employed a 2 × 2 factorial design in which participants received erythropoietin or transfusion at different thresholds. We were unable to isolate the effects of transfusion from erythropoietin |
| Vichinsky 1995 | RCT. Ineligible intervention. The transfusion trigger was based on the level of sickle haemoglobin, not the haemoglobin or haematocrit level |
| Voorn 2017 | RCT. Ineligible intervention (trial focused on educating clinicians to cease to use preoperative erythropoietin and perioperative autologous blood salvage, rather than transfusion thresholds) |
| Yamada 2020 | Ineligible design. Survey of details on antigen‐positive RBC transfusions (826 cases from 45 institutions) |
| Zygun 2009 | RCT. Eligible intervention. Ineligible focus ‐ this trial measured oxygen utilisation and planned no clinical outcomes of interest |
Abbreviations
ICU: intensive care unit RBCs: red blood cells RCT: randomised controlled trial