Systematic reviews and meta-analyses comparing mortality in restrictive and liberal haemoglobin thresholds for red cell transfusion: protocol for an overview of systematic reviews.

Introduction: There has been a significant increase in the number of systematic reviews and meta-analyses of randomised controlled trials investigating thresholds for red blood cell transfusion. To systematically collate, appraise and synthesise the results of these systematic reviews and meta-analyses, we will conduct an overview of systematic reviews.
Methods and Analysis: This is a protocol for an overview of systematic reviews. We will search five databases: MEDLINE, Embase, Web of Science Core Collection, PubMed (for prepublication, in process and non-Medline records) and Google Scholar. We will consider systematic reviews and meta-analyses of randomised controlled trials evaluating the effect of haemoglobin thresholds for red blood cell transfusion on mortality. Two authors will independently screen titles and abstracts retrieved in the literature search and select studies meeting the eligibility criteria for full-text review. We will extract data onto a predefined form designed to summarise the key characteristics of each review. We will assess the methodological quality of included reviews and the quality of evidence in included reviews.
Ethics and Dissemination: Formal ethics approval is not required for this overview as we will only analyse published literature. The findings of this study will be presented at relevant conferences and submitted for peer-review publication. The results are likely to be used by clinicians, policy makers and developers of clinical guidelines and will inform suggestions for future systematic reviews and randomised controlled trials.
Prospero Registration Number: CRD42019120503.
Competing Interests: Competing interests: SLF reports other financial support from National Blood Authority (Australia), non-financial support from Medical Society for Blood Management (Europe), non-financial support from Health Round Table (Australia) and non-financial support from University of Tasmania, Australia, outside the submitted work. JI is chair of the Australian National Blood Authority Patient Blood Management Implementation Committee. AH reports personal fees from the Austrian Institute of Technology, Austria; personal fees and non-financial support from TEM Innovations, Germany; personal fees and non-financial support from Vifor Pharma International AG, Switzerland; personal fees and non-financial support from Hamoview Diagnostics, Australia; personal fees from Thieme Publishing, Germany; personal fees and non-financial support from UCB Pharma, PR of China; personal fees from Vygon SA, France; personal fees and non-financial support from Vifor Fresenius Medical Care Renal Pharma Ltd, Switzerland; personal fees and non-financial support from Swiss Medical Network, Switzerland; and non-financial support from South African National Blood Service, South Africa, outside the submitted work.
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