At the UMHS Histocompatibility Laboratory potential recipients are typed for HLA-A, B, C, DRB1,3,4,5, DQB1, DQA1 loci by medium/low resolution SSO molecular methods. Each recipient is screened to detect preformed anti-HLA antibodies. Patients may develop these antibodies in case of previous sensitization events like transfusion, 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% and the Unacceptable Antigens list in the UNOS database every 3 months. Every month a fresh serum sample is mailed to the Organ Procurement Organization (OPO). This serum sample and the historic higher PRA% sample (peak) will be used for Flow Cytometric Crossmatch with matched deceased donors.