What is primarily at risk if histocompatibility testing is not performed?

Histocompatibility testing plays a crucial role in evaluating the compatibility between donor and recipient tissues or organs. The primary concern when this testing is not conducted is the increased risk of tissue rejection. This occurs because the immune system may recognize the transplanted tissue as foreign, leading to an immune response that can damage or destroy the transplanted tissues.

When histocompatibility testing is appropriately performed, it helps ensure that the donor's human leukocyte antigens (HLA) match those of the recipient as closely as possible, thereby reducing the likelihood of an adverse immune reaction. Without this important assessment, incompatible grafts may be more likely to fail due to rejection, which can have serious implications for patient health and the success of the transplant procedure.

Other options, while potentially impacted by the lack of histocompatibility testing, do not directly reflect the immediate and critical consequence associated with not performing this essential evaluation. Hence, the risk of tissue rejection stands out as the foremost concern in the context of transplant success.