Three matching tests, blood typing, tissue typing and cross-matching, are required before a kidney transplant can be performed. The blood typing test means that the ABO blood types of the kidney transplant recipient and the kidney donor need to match. As a special case the blood type of the kidney donor is O and the blood type of the person who needs a kidney transplant is other blood type, the kidney donor can be used as an alternative. After the blood grouping is completed, tissue typing of the kidney donor and recipient is required, mainly to detect the number of antigens shared by the donor and recipient, antigens that identify differences between the body tissues of the two individuals. The match is at least 50% for parents and children, and zero to 100% for siblings. The best match for a recipient is one in which all six antigens match each other. A cross-match test is required and the recipient will have at least two different times to see if there will be a reaction to the donor kidney. If there is no reaction, the result is negative for cross-matching, indicating that the transplant can be performed. These three tests are essential matching tests during the transplant matching process.