Investigating the association between blood transfusion and clinical outcomes in patients with acute coronary syndromes: a data linkage approach to Patient Blood Management

Background: The appropriateness of the use of blood transfusion in patients with acute coronary syndromes (ACS) remains contested. In general, studies addressing this issue were based on data from clinical trials, registries, or electronic medical records, and were conducted across different settings. Our study aimed to use a linked patient blood management data system from existing hospital databases to examine the association between blood transfusion and in-hospital mortality, length of stay (LOS) and readmission rates among patients with ACS, and to investigate this relationship at different haemoglobin (Hb) concentrations.

Materials and methods: This was a retrospective observational study of patients admitted to participating hospitals between 1st January 2014 to 31st December 2017 with ACS recorded as primary diagnosis. Admission and nadir Hb concentrations were categorised as ≤100 g/L and >100 g/L. Generalised estimating equations were used to investigate the association between transfusion and clinical outcomes, while accounting for the correlation of multiple admissions from the same patients across hospitals over the study period.

Results: Of the 9,952 admissions included, blood transfusions occurred in 705 (7.1%). In unadjusted analyses, transfusion was associated with an increased risk of in-hospital mortality (OR: 2.97; 95% CI: 2.14-4.13) and an average LOS 3.55 (95% CI: 3.38-3.72) times longer. After adjusting for demographic and clinical factors, transfusion was associated with an increased risk of in-hospital mortality when Hb >100 g/L. Transfusion was not associated with the risk of readmission.

Discussion: The effect of transfusion on in-hospital mortality was largely dependent on the pre-transfusion Hb concentration. When Hb was >100 g/L transfusion was associated with increased mortality, whereas when Hb ≤100 g/L no association was observed.