The role and importance of epidemiology in transfusion medicine.

Transfusion therapy is an indispensable form of treatment, and an important element of the public health system. Due to its origin, blood's clinical use is associated with various risks that may cause adverse reactions and events. Progress in quality and safety of blood components has eliminated numerous risks, especially those of infectious origin. However, some risks cannot be predicted, while others cannot always be prevented. Globalisation and climate change constantly favour the spread of infectious agents. Against this, epidemiology plays a central role in ensuring the safety of transfusion treatment, by continuous surveillance and timely identification of risks, and in the development of routine and additional tests as measures for risk mitigation. As a quantitative discipline based on research methods, epidemiology is a method of reasoning; it relies on the generation and testing of hypotheses; it utilises other scientific resources, particularly in the field of blood donation and blood transfusion, thus having many applications. The main focus falls on transfusion-transmissible infections, and on environmental or occupational diseases, injuries, disabilities and death causes at large. The practice of epidemiology relies on a systematic approach and measurement of disease frequencies. Surveillance is a key element, involving continuously gathering, analysing, and evaluating data regarding diseases, morbidity and mortality, and disseminating the conclusions of the analyses to relevant competent authorities; in this way, action is taken for disease prevention and control. Surveillance systems also provide an important tool for risk assessment, a method to assess and characterise the critical parameters in the functionality of equipment, systems or processes of using scientific data in order to estimate the magnitude of any health effect that derives from decisions of policy makers. Epidemiological surveillance, particularly for the incidence of adverse reactions and adverse events associated with blood transfusion at the national and international levels, has demonstrated the importance of multidisciplinary cooperation between blood and public health services.