Final answer:
C) Clerical errors are the primary cause of noncompatible transfusions when there is incorrect identification of blood types. This can result in severe transfusion reactions, including agglutination and hemolysis due to the immune system attacking the mismatched blood cells.
Step-by-step explanation:
The primary causes of noncompatible transfusions, which can be life-threatening to patients, are largely due to clerical errors. Such errors involve misidentification of blood types resulting from incorrect labeling, documentation, or interpretation. For example, if a person with type B blood receives a type A blood transfusion, their immune system will react negatively. This is because the recipient's anti-A antibodies will agglutinate the donor's A antigen-bearing red blood cells. Furthermore, this interaction activates the classical complement cascade, leading to a severe inflammatory response and massive hemolysis of the transfused red blood cells.
An antibody screening test is typically performed with pretransfusion blood typing to ensure the compatibility of the blood recipient's ABO and Rh blood group system. Hence, Clerical errors are most often the cause for noncompatible blood transfusions, not issues such as bacterial contamination, excessively clumped platelets, or expired crossmatch test tubes.