Assessing the clinical relevance of the suspected HTLA antibody is an essential piece of the puzzle. When crossmatch-compatible units are identified in the anti-human globulin (AHG) phase, prioritizing these units is recommended. If the antibody's specificity has been established through chemical or enzyme treatments, neutralization, or the use of rare red cells lacking a high-prevalence antigen, it is prudent to consult current literature, such as the latest AABB Technical Manual, to understand its clinical implications.
Selecting red cells that are compatible with the patient's ABO and Rh type is generally considered safe in cases where the antibody does not cause adverse reactions but compatible crossmatches are not available. Similarly, choosing antigen-negative blood is advisable in cases where the antibody is known to cause adverse reactions.
If the antibody's identity is still unknown, or its clinical significance is either in question or known to be variable according to the literature, then the transfusion decision needs to be made by the laboratory medical director and the attending physician. A helpful tool to assist with this decision that can be recommended to the physician is the monocyte monolayer assay (MMA) test. The MMA test predicts the likelihood of a hemolytic reaction following transfusion with crossmatch-incompatible blood and is often used when rare antigen-negative blood is not readily available. It achieves this by measuring the degree of phagocytosis that occurs after monocytes are activated when the antibody binds to the red cell antigens.
