I was surprised to learn that the major use of donated blood is helping people with cancer and blood diseases. Just 2% of red blood cells are used to treat trauma patients, including those involved in road accidents. Most of us would know how important it is to correctly match the blood group type of donor and patient, but not be aware of the details. For a highly understandable article on the ABO and Rhesus blood group systems, it would be hard to improve on this article by Ashley Ng, Post Doctoral Fellow and Haematologist at Australia's oldest Medical Research Institute, the Walter and Eliza Hall Institute, Melbourne, Australia. Coincidentally this institute celebrates it's centenary next year, a period just slightly less than that in which blood typing has been saving lives.
For a snapshot view of how donated blood is used, check out this page by the Australian Red Cross:
Note that donated blood use is categorised into three groups: red cells, plasma and platelets. We may need blood products from each of them to improve our quality of life while on Watch and Wait as well as to possibly save our lives during treatment, by helping us recover from anaemia, boost our immunity (IVIG transfusions) or boost falling platelet levels.