BASEL, Switzerland, June 24, 2020
In a study that is the first of its kind, researchers from the University of Western Australia analyzed a massive amount of data on death rates from all systematic reviews of clinical trials comparing restrictive and liberal transfusion strategies. The landmark study, known as an Overview of Systematic Reviews, combined data from 19 reviews of 53 unique clinical trials published between 1956 and 2017. The results are published online today in the journal BMC Medicine. (Systematic reviews and meta-analyses comparing mortality in restrictive and liberal haemoglobin thresholds for red cell transfusion: an overview of systematic reviews)
Speaking about the study, lead author Mr. Kevin Trentino said, "Our comprehensive search through the medical literature summarized vast amounts of data from reviews of clinical trials, making it an ideal starting point for clinicians and guideline developers interested in transfusion practice research."
The results tell an interesting story. Back in 1999, researchers from Canada published a landmark clinical trial investigating the impact of delaying the decision to transfuse until a patient's blood levels decreased to lower levels than previously considered necessary for patient safety (known as a restrictive strategy). The results challenged long-held beliefs about transfusion, as the authors found no benefit to patients assigned to a more liberal transfusion strategy. In fact, in some measures, patients assigned to the restrictive transfusion group, who received less blood, did better.
"It is interesting that 20 years later, with over 50 additional clinical trials, we are still drawing the same conclusions,"Prof Aryeh Shander an IFPBM scientific associate said. "We found that three quarters of studies found no difference in death rates between groups, and one quarter found death rates were lower in those assigned to a restrictive transfusion strategy."
Lead author, Trentino, also stated that this exhaustive review identified a number of serious limitations with the included reviews and clinical trials. "The issues we identified are relevant because they resulted in smaller than expected differences in transfusions between groups studied, skewing results towards no differences in mortality. These limitations would need to be taken into account with the conducting of future trials and reviews to enable a better understanding of transfusion strategy's impact on patient outcomes."
The results of this work are especially timely in the context of the current COVID-19 pandemic. "Across the world medical care is experiencing blood supply challenges with a significant drop in donations due to the pandemic," co-author Dr Shannon Farmer said. "This study provides some of the highest evidence supporting a recent global call for action from over 43 international experts for immediate implementation of better patient blood management." (The Essential Role of Patient Blood Management in a Pandemic: A Call for Action)