Harmonizing the definition of massive transfusion used in clinical trials.

Abstract

Background: Major haemorrhage requiring massive transfusion (MT) can occur in almost any clinical setting. However, no universal MT definition currently exists, making comparisons between studies/ services difficult. Aim(s): In this first systematic review (SR) on the topic, we aimed to identify MT definitions used in RCTs across various specialties to inform development of a consensus definition. Method(s): A comprehensive search was performed in MEDLINE, Embase, Cochrane Library, PubMed, CINAHL, and Transfusion Evidence Library for studies from inception until 10 March 2021, with no language restriction. Inclusion criteria were: (1) RCT or SR with >=1 RCT; (2) individuals >=18 years with major bleeding who had received or were anticipated to receive MT in any clinical setting; (3) specified a definition for MT as either an intervention or outcome. Conference abstracts, commentaries, post-hoc analyses and studies including only non-human subjects or platelet transfusions were excluded. Result(s): Of 5760 distinct references identified from the initial search, 33 studies were included for preliminary analysis (20 RCT, 13 SR), with an additional 16 unable to be sourced and 19 awaiting translation. The studies pertained to 3 clinical settings (trauma [n = 26], surgery [n = 6], obstetrics [n = 1]) and covered diverse geographical locations (multinational [n = 6], Europe [n = 8], Asia [n = 1], Oceania [n = 4], Africa [n = 1], Americas [n = 14]). The most frequently used MT definition was >=10 units (U) red blood cells (RBC)/24 h (h) (n = 13), followed by >10 U RBC/24 h (n = 6). The remaining studies used assorted definitions including >=3 U RBC/1 h, >=4 U RBC/4 h, >=5 U RBC/4 h or 24 h, >5 U RBC over an unspecified time, >6 U/48 h, 10 U/6 h or 12 h, >=12 U blood/12 h, and >20 U blood over an unspecified time. Summary/Conclusions: Significant heterogeneity exists in MT definitions across RCTs. Definitions most commonly featured units of RBCs over a time period, with no mention of other blood components. A standardized definition for MT is urgently needed. (Table Presented).