Leukoreduction is a process by which leucocytes are removed from donated blood. The usual level of leukoreduction to prevent the febrile non-hemolytic transfusion reaction (FNHTR) is 0.5x108 i.e. 1 log reduction, this is known as critical antigenic leukocyte load which can be achieved by removing buffy coat. However, for preventing alloimmunization or transmission of viruses like CMV the residual leukocyte level should not be more than 5x106, this is called critical immunogenic leukocyte load. Leukodepleted blood components are commonly manufactured via filtration. In the 1980s, advancement in technology led to the development of different generation of filters, with a leukocyte removal efficiency upto 98 percent.