A retrospective analysis of the value of monocyte monolayer assay results for predicting the clinical significance of blood group alloantibodies

Abstract

Cellular assays (e.g., monocyte monolayer assays [MMAs]) have been used to predict the clinical significance of red blood cell (RBC) alloantibodies. Twenty years of MMA data were retrospectively analyzed to 1) determine the optimal cut point (by correlating MMA results from 46 patients with RBC survival study results and/or laboratory and clinical signs of hemolytic transfusion reactions [HTRs] when incompatible blood was transfused), and 2) determine what percentage of 251 unusual alloantibodies (most to high-incidence antigens) were predicted to be clinically significant. Two MMA cut points (5% and 20%) were chosen using a receiver-operating characteristics curve. No patients with MMA results less than or equal to 5 percent had clinical signs of a reaction; one-third of patients with MMA results 5.1 to 20 percent versus two-thirds with results greater than 20 percent had clinical signs of a HTR after transfusion of incompatible blood. Using 5-percent or 20-percent cut points, 173 (69%) or 97 (39%) of 251 unusual alloantibodies gave positive MMAs, respectively. A negative MMA (< or =5%) indicates that incompatible blood can be given without risk of an overt HTR but does not guarantee normal long-term survival of those RBCs. Most unusual alloantibodies are predicted to cause shortened RBC survival, but transfusion of incompatible blood may not result in any clinical or laboratory signs of a HTR. We have used the MMA for approximately 20 years, instead of a 1-hour chromium-51 RBC survival, to aid in the decision to transfuse RBCs incompatible with antibodies to high-incidence antigens.