Transfusion thresholds and beyond.

To transfuse or not to transfuse: that is the question! And this is a longstanding issue that has to be faced if we want to consider allogeneic blood transfusion to be a lifesaving procedure. It does, however, involve several risks, including infectious (viral and bacterial) complications, transfusion-related acute lung injury, ABO- and non-ABO-associated haemolytic transfusion reactions, transfusion-associated Graft-versus-Host disease, and transfusion-associated circulatory overload1. These complications represent the principal causes of allogeneic blood transfusion-related morbidity and mortality. Over the last thirty years, this has led to a number of randomised controlled trials (RCTs) being carried out aimed at comparing the effect on patients of restrictive (haemoglobin concentration 7–8 g/dL) with more liberal (haemoglobin concentration approximately 10 g/dL) blood transfusion strategies in a variety of clinical settings2. In parallel, a number of systematic reviews and meta-analyses3–10 have been conducted with the aim of performing a pooled analysis of the data from these RCTs (see Table I for a summary of results).