Abstract
BackgroundThere are no overviews of systematic reviews investigating haemoglobin thresholds for transfusion. This is important as the literature on transfusion thresholds has grown considerably in recent years. Our aim was to synthesise evidence from systematic reviews and meta-analyses of the effects of restrictive and liberal transfusion strategies on mortality.MethodsThis was a systematic review of systematic reviews (overview). We searched MEDLINE, Embase, Web of Science Core Collection, PubMed, Google Scholar, and the Joanna Briggs Institute EBP Database, from 2008 to 2018. We included systematic reviews and meta-analyses of randomised controlled trials comparing mortality in patients assigned to red cell transfusion strategies based on haemoglobin thresholds. Two independent reviewers extracted data and assessed methodological quality. We assessed the methodological quality of included reviews using AMSTAR 2 and the quality of evidence pooled using an algorithm to assign GRADE levels.ResultsWe included 19 systematic reviews reporting 33 meta-analyses of mortality outcomes from 53 unique randomised controlled trials. Of the 33 meta-analyses, one was graded as high quality, 15 were moderate, and 17 were low. Of the meta-analyses presenting high- to moderate-quality evidence, 12 (75.0%) reported no statistically significant difference in mortality between restrictive and liberal transfusion groups and four (25.0%) reported significantly lower mortality for patients assigned to a restrictive transfusion strategy. We found few systematic reviews addressed clinical differences between included studies: variation was observed in haemoglobin threshold concentrations, the absolute between group difference in haemoglobin threshold concentration, time to randomisation (resulting in transfusions administered prior to randomisation), and transfusion dosing regimens.ConclusionsMeta-analyses graded as high to moderate quality indicate that in most patient populations no difference in mortality exists between patients assigned to a restrictive or liberal transfusion strategy.Trial registrationPROSPERO CRD42019120503
Highlights
There are no overviews of systematic reviews investigating haemoglobin thresholds for transfusion
Meta-analyses graded as high to moderate quality indicate that in most patient populations no difference in mortality exists between patients assigned to a restrictive or liberal transfusion strategy
There may be limits to generalisability in some specific patient populations, the results from these studies indicate that a restrictive compared to a liberal transfusion strategy in most patient populations reduces the number of patients exposed to red cell transfusion and the number of red cell units transfused, and show that no difference in mortality exists
Summary
There are no overviews of systematic reviews investigating haemoglobin thresholds for transfusion. Our aim was to synthesise evidence from systematic reviews and meta-analyses of the effects of restrictive and liberal transfusion strategies on mortality. In 1999, the Transfusion Requirements in Critical Care trial [1] was published This trial randomised critical care patients to either a restrictive or liberal red blood cell transfusion strategy. Patients assigned to the restrictive strategy were transfused if their haemoglobin concentration dropped below 70 g/L and concentrations were maintained at 70 to 90 g/L. Patients assigned to the liberal strategy were transfused if their haemoglobin concentration dropped below 100 g/L with concentrations maintained at 100 to 120 g/L. Many randomised controlled trials (RCTs) evaluating restrictive and liberal red cell transfusion strategies in a variety of patient populations have been published. Systematic reviews and meta-analyses synthesising the results of these trials were conducted
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