In developed countries considerable effort and resources have been devoted to refining donor screening and blood testing. This has reduced the risk of known infectious agents such as HIV, HCV and HBV being transmitted via blood transfusion to very low levels.

In developing countries, however, viral risk is an ongoing challenge. It has been reported that only 43% of WHO member nations (191) test for the above agents. This means that of the estimated 75 million units donated each year worldwide, 13 million units are not tested prior to transfusion.

Despite increased viral safety in developed countries, the blood supply remains vulnerable to new and new strains of existing infectious agents. It has been estimated that a new infectious agent emerges every three years. In recent years, numerous agents have been identified as potential threats to the blood supply. In addition to bacterial, protozoan and prion agents, several newly discovered hepatitis viruses present unique challenges in assessing possible risks they may pose to the safety of blood and plasma products.

Highlighting the challenge represented by emerging agents, Dr Harvey Klein of the National Institutes of Health, USA, stated: “It is sobering to consider that if a new agent with a long silent carrier state and efficient blood transmission (HIV prototype) were to appear, the blood component collectors would be scarcely better prepared to interdict a transfusion-transmitted epidemic than they were during the early days of AIDS in 1977.” (Emerging Infectious Disease and Blood Transfusion: The Coming Plague. TATM 2005;7(1):18.)

In addition to infectious risks, there are immunological and allergic reactions to blood. Some of these are mild and relatively harmless while others are more severe and potentially fatal.

Multiple handling procedures involved in a transfusion has receiving the wrong blood a risk despite efforts to address the problem. According to the 2004 Serious Hazards of Transfusion (SHOT) report, there was a 26% increase in the number of “wrong blood” transfused incidents reported. However, the number of ABO incompatible transfusions, the most serious and potentially fatal error, decreased during that period. More than 50% of identifiable transfusion-related deaths are a result of incorrect blood component transfused.

Greater safety issues may relate to evidence for an immunomodulatory and proinflammatory effect from transfusion and negative clinical consequences from storage related problems. Studies have shown an association between transfusing stored blood and increased mortality, morbidity, intensive care unit (ICU) and hospital stay and increased hospital costs.

Recent concerns have focused on the growing awareness of transfusion-related acute lung injury (TRALI). Under-recognized and poorly understood, TRALI has been the leading course of transfusion-related-death reported to the FDA in the United States for the past 2 years. Researchers suggest TRALI’s pathogenesis is multifactorial, with the negative effects of storage and immunomodulation possibly implicated.