How low can we go? Comparison of liberal and restrictive red cell transfusion thresholds in paediatric allogeneic haematopoietic stem cell transplantation: A randomized multicentre feasibility trial.

Optimal red blood cell transfusion thresholds for children with bone marrow failure are uncertain; a previous study was stopped following concerns about veno-occlusive disease. The aims of this study in allogeneic haematopoietic stem cell transplant (HSCT) were to assess feasibility of recruitment and protocol adherence (primary outcomes) for different haemoglobin (Hb) transfusion thresholds, and to describe safety and present exploratory data on quality of life (QoL). Children aged ≥1 to <18 years were randomized to restrictive Hb transfusion thresholds of 65 g/L (restrictive) vs. 80 g/L (liberal) for HSCT days 0-100. Thirty-four patients were randomized at four UK HSCT centres, 17 in each arm. 48.6% (34/70) of eligible patients were recruited (target ≥50%), with high levels of protocol adherence: % (n/N) [95% CI] in the restrictive and liberal arms were 99.2 (961/969) [98.6, 99.7] and 97.2 (1131/1164) [96.2, 98.1] respectively (target ≥70% each arm). The mean pre-transfusion Hb was 16.3 g/L higher in the liberal than in the restrictive arm. Feasibility to measure QoL was demonstrated with no evidence of more fatigue in the restrictive arm. Although the study was not powered for clinical outcomes, the findings suggest that some populations may be able to safely tolerate anaemia levels below 70 g/L, the most common restrictive transfusion threshold.