The International Haemovigilance Network's (IHN) ISTARE database collects surveillance data on all adverse reactions (AR) associated with transfusion of blood and blood components, facilitating the sharing of best practice and benchmarking for improving blood safety and quality. Up to 2012, no publications discussed certain rare AR. The aim of this study is to examine ISTARE data on AR from 2012 to 2016, focusing on hypotensive reactions, post-transfusion purpura (PTP), transfusion-associated graft versus host disease (TA-GvHD), hyperkalemia and hypocalcemia.

National Haemovigilance Systems (HVS), provided aggregate annual data on AR by type of reaction, severity, imputability to transfusion, and blood component implicated. Twenty-nine HVS provided 104 annual reports covering 107,778,290 blood units issued.

Among AR reported, 25% were serious, including 368 deaths. The 284 transfusion-transmitted infections included 187 bacterial infections, 84 viral and 13 parasitic or fungal; nine deaths resulted. AR related to the respiratory system transfusion-associated circulatory overload, transfusion-related acute lung injury and transfusion-associated dyspnoea accounted for 8.3% of all AR, 20.1% of serious, and 52.2% of deaths. Of 1634 rare AR, 1565 were hypotensive, 38 PTP, 17 GvHD, 9 hyperkalemia and 5 hypercalcemia. Half were serious and 16 fatalities were recorded (13 hypotensive, 2 GvHD, one PTP). Among 14 countries that reported any hypotensive AR, incidences diverged widely.

ARs in this group are frequently severe or life-threatening. Hypotensive AR are the most common, but may have been overlooked and counted under allergic and other AR presenting with hypotension. Compliance with the ISBT definition may be suboptimal, thus its real incidence may be higher. Data on GvHD may contribute to clarifying the role of leukodepletion with or without irradiation. ISTARE continues to be a useful surveillance tool for all transfusion AR and provides relevant insights into overlooked and rare AR, thus offering important contributions towards maximising transfusion safety.