Introduction: Transfusion Associated Circulatory Overload (TACO) is a leading cause of transfusion related adverse events. Existing estimates of TACO incidence are derived from observations in a predominantly inpatient setting, where, incidence estimates range from 1 to 8% of transfusions (Bachowski G, et al. A Compendium of Transfusion Practice Guidelines Third Edition 2017: American Association Blood Banks). This is the first report of incidence and risk factors for TACO in ambulatory transfusions.

Methods: A retrospective cohort analysis of ambulatory patients transfused in a tertiary haematology centre was undertaken in a 12 month period between January to December 2014. Electronic medical records, electronic transfusion database, and patient notes were utilized to obtain data. Variables included age, gender, haematological diagnosis, documented congestive heart failure (CHF) or chronic kidney disease (CKD), details of transfusion encounter, and post transfusion medical review. For the purpose of this study, TACO was defined as documented evidence of hypervolaemia on clinical review and/or if otherwise unplanned diuretic therapy was prescribed for symptoms/signs of fluid overload.

Logistic regression models were used to measure associations between TACO events and patient covariates, using cluster-robust Huber-White standard errors to account for the repeated observations on patients. Variables were selected for entry into the statistical models based on a review of existing evidence. Statistical analyses were programed using Stata v13.0 (StataCorp Ltd, College Station, Tx) and was approved by institutional ethics committee.

Results: A total of 812 transfusion encounters in 94 ambulatory patients (male=50, female=44), with a mean age of 76 ±11.3 years was observed. The most common underlying haematological diagnoses included myelodysplasia, myelofiborisis, acute leukemia, (table 1). At baseline, 11.2% (14/94) and 13.6% (17/94) of subjects had documented history of CHF and CKD (table 1).

There was a total of 1723 packed red cell units (PRBC) transfused across the 812 ambulatory transfusion encounters. The median number of units transfused was 2 per encounter (range 1-4) and median cumulative number of transfusions received per patient was 7 (range 1-28) over the study period. TACO was observed in 7.03% of all transfusion encounters (a total of 57 events in 32 subjects).No cases resulted in inpatient investigation, management or death.

The variables of age, gender, CHF, CKD, PRBC units per encounter, and cumulative units received were assessed in regression models. In a univariate model, age was observed to be significantly associated with TACO, odds ratio=1.048 (p=0.011 95%, CI 1.011-1.086).The remaining variables were not statistically significant predictors of TACO in either univariate or multivariate model and significance for age was not retained in a multivariate model (p=0.06) as shown in table 2.

Conclusions: This data confirms TACO is an important consideration in the ambulatory transfusions and occurred in 7.03% of transfusion encounters. This is similar to the range seen in hospitalized patients though it was reassuring that no severe cases were observed. Patient age appeared to be an important risk factor in the univariate model with the odds for TACO increasing with each year. In contrast to hospitalized patients, CHF and CKD did not increase the odds for TACO in multivariate regression models. To our knowledge, this is first study to report on incidence and risk factors for TACO in ambulatory transfusions providing a new perspective on this important aspect of haemovigilance. These results also enable better patient information prior to consenting for transfusions. Our study is limited by the retrospective and single center design, but provides vital baseline data for future prospective studies.


No relevant conflicts of interest to declare.

Author notes


Asterisk with author names denotes non-ASH members.