The monocyte monolayer assay, an in vitro method for prediction of in vivo survival of transfused incompatible red blood cells: a review

It has long been a goal of transfusion medicine scientists to predict which patients will make clinically significant antibodies when transfused with donor red blood cells (RBCs). But this goal has yet to be achieved. Not all patients have an adverse response to an RBC transfusion by making an antibody to an RBC antigen, and for patients who do, in most cases, they form antibodies to common antigens for which provision of antigen-negative RBCs is not difficult. However, for patients who make antibodies to many antigens and for patients who make an antibody requiring rare blood that is negative for a high-prevalence antigen, knowing the clinical significance of that patient’s antibody is important for effective and timely transfusion. This review of the literature provides information on the monocyte monolayer assays (MMAs) developed to predict the outcome of incompatible RBC transfusion. One of these assays has been used for almost 40 years in the United States to predict the outcome of RBC transfusion in patients with alloantibodies for whom provision of rare RBCs is very difficult. Because all transfusion medicine facilities and blood centers will not likely implement the MMA, it is important that the selection of the referral laboratory be carefully made. The MMA is a proven test in the prediction of incompatible transfusion outcomes in patients with IgG-only antibodies. It has been helpful in decision-making when rare blood components are not available or not available quickly, although decisions on blood transfusion must be made by the physician attending the patient and blood should not be withheld waiting for the MMA result in an urgent situation.