Each recipient is screened to detect preformed anti-HLA antibodies. Patients may develop these antibodies in cases of previous sensitization events like transfusions, pregnancies, or previous transplant. When these antibodies are detected the Panel Reactive Antibody (PRA%) value is assigned and the anti-HLA antibody specificity is defined by Solid Phase Single Antigen assays. PRA% values are updated with a new sample every 3 months. For patients listed for transplant with a deceased donor the Histocompatibility Laboratory will updated PRA% every 3 months.