Stands for con­fir­ma­to­ry typ­ing: addi­tio­nal tes­ting per­for­med as part of the search for a donor. The HLA cha­rac­te­ris­tics of the donor and pati­ent are ana­ly­zed again to veri­fy the match. Sero­lo­gy tes­ting for infec­tions (e.g. for hepa­ti­tis C and HIV) is often car­ri­ed out in parallel.