My sister and I are being transplanted in 2 weeks. Our transplant nurse coordinator called today to arrange for our final crossmatch next week. Why do we have to repeat the crossmatch? We did it 3 months ago

We repeat the crossmatch to be sure that you have not developed any antibodies to your sister’s antigens. It is not always possible to identify a particular reason why the HLA antibodies are present, and they can appear and disappear from the serum quickly. Therefore it is necessary to perform a crossmatch close to the time of actual transplantation even if the crossmatch between a particular donor and recipient has been negative in the past. If you had an infection in the last 3 months or received a blood transfusion, you may have developed some new antibodies that may be directed against your sister’s antigens. If you have developed antibodies toward your sister’s antigens, you may reject her kidney after surgery.