The four items need to be checked before blood transfusion is to exclude whether the body carries virus or not, and by doing blood four items check, it can avoid abnormal situation after blood transfusion. The four items of pre-transfusion examination include hepatitis C antibody, hepatitis B surface antigen, syphilis antibody, AIDS antibody, etc. Through the above four examinations, it is possible to know whether the body carries the above viruses or not. If there is no virus before transfusion but the body is infected with the virus after transfusion, it is necessary to have a high suspicion of viral infection caused by blood transfusion, which is more conducive to further finding the source of infection. When performing the pre-transfusion test, it is important to choose a regular medical institution and to work with a skilled doctor to perform the test.