Outpatient Red Cell Transfusion in Patients with Blood disorders or Cancer: The difference between one or two units of red blood cell concentrates

There are significantly fewer studies on red blood cell (RBC) transfusion in the outpatient setting than in the inpatient setting. In this retrospective study, we investigate factors influencing transfusion strategy and transfusion triggers in outpatients. The here presented data, focused on the comparison of a strategy of transfusion of one (n=919 visits) versus two RBC (n=2752 visits) in outpatients with cancer or blood disorders (n=571).

Data on outpatient RBC transfusions performed in the years 2021 and 2022 were retrospectively collected in a single centre. Multiple linear regression or multiple logistic regression was used to determine factors that contribute to decision making for RBC transfusion. For the logistic regression data is given as Odds Ratio (OR) and 95% confidence intervals. Data are given as median and interquartile ranges if not stated otherwise. N=778 patients with n=7296 visits are included in the whole cohort of the study. One unit was transfused in n=919 visits and 2 units in n=2752 visits.

The strongest factor to avoid RBC transfusion was a higher Hb with an OR of 0.13 (0.11-0.14). The OR was highest for fatigue (6.0, 4.9-7.3) and dyspnoea (2.1, 1.7-2.8). Increased OR was observed for concomitant heart disease (1.6, 1.3-2.0) and male sex (1.3, 1.1-1.6). Age had a minor effect (1.04, 1.03-1.04). Two instead of 1 RBC units were more likely to be given in females and patients with dyspnoea, fatigue or cytopenia. Selecting episodes with transfusion intervals ≤ 28 days showed distances of 9 days after 1 RBC and 14 days after 2 RBC units. A linear modelling showed shorter intervals in males, in cases with lower post-Hb levels, lower reticulocyte counts and presence of dyspnoea, concomittant transfusion of Plts and administration of 1 instead of 2 RBC units. In this model the transfusion of 2 instead of 1 RBC units prolonged the interval by 2.1 days.

This is the largest published cohort in outpatient transfusions. Different factors contribute to the transfusion of RBC with Hb-level and the occurrence of symptoms among them. Transfusion intervals were shortened by accompanying Plt transfusions, male sex and lower Hb. The potential of reducing RBC units by a strategy of administering 1 unit per visit can be estimated at 21-42% based on our retrospective data. However, this potential needs to be determined in a prospective clinical trial.

All authors are employed by a blood transfusion service.