What does 'cross-matching' ensure in blood banking?

Cross-matching is a critical procedure in blood banking that focuses on ensuring compatibility between a patient and a donor's blood. This process involves mixing a small sample of the patient's blood with the donor's blood to observe any reactions. When the blood from the donor and recipient is mixed, the laboratory can observe whether the blood cells agglutinate or clump together, indicating that the blood types are not compatible. Ensuring compatibility is vital because a transfusion of incompatible blood can lead to serious, potentially life-threatening reactions in the patient.

While testing for infectious diseases is an important part of blood banking, it does not address compatibility. Checking blood types is related but is only a preliminary step and does not confirm compatibility on its own, as it doesn't account for additional factors like antibodies in the patient's blood. Verifying the purity of blood samples is also essential but does not pertain to ensuring the safety of a transfusion regarding patient compatibility, which is what cross-matching specifically addresses.