evaluation of alloimmunization rate and necessity of blood type and screening test among patients candidate for elective surgery.

introduction: alloimmunization is a reaction of the immune system to foreign antigens. for prevention of alloantibody formation, performing of type and screen test is necessary on a patient's blood specimen as part of pre-transfusion testing. materials and method: in this cross-sectional study, type and screen test done for 1420 patients with elective surgery for detection of alloantibody in imam khomeini hospital in ardabil. results: prevalence of alloantibody in this population was 0.92% (13 patients) and 99.2% (1407 patients) showed no alloantibody in their serum. the most prevalent alloantibody was anti-k, anti-e and anti-c. no significant relationship observed between sex and alloimmunization rate. conclusion: performance of type and screen test play an important role in reducing the rate of alloimmunization, and also, could reduce the demands for blood reservation in hospital blood banks.