Transplant candidates who have received a transplant or blood transfusion, or have been pregnant, may be sensitized. Serum screening for alloreactive antibodies against a random cell panel will provide an assessment of the degree of sensitization, expressed as the percentage panel reactive antibody. The panel reactive antibody can be vary between 0% (nonsensitized) and 80% to 100%, indicating a high degreee of sensitization. Patients with high panel reactive antibody values are less likely to have crossmatch-negative donors. They must wait much longer for a transplant, and some may never receive a kidney.