A comparison of the monocyte monolayer assay with 51 chromium red cell recovery for determining the clinical significance of red cell alloantibodies

The 51 chromium ( 51 Cr) red cell recovery study is a reliable measure of transfusion compatibility. However, the monocyte monolayer assay (MMA) does not require the use of radioactive isotopes or the injection of incompatible RBCs. In this study, 51 Cr recoveries were performed on 12 patients with well-defined antibodies, and the results compared to the MMA procedure. The MMA method was interpreted by counting the percentage of monocytes with associated RBCs (>3% = positive). The MMA correlated with the 51 Cr recovery in 11 of 12 subjects. One anti-K1 that caused moderately accelerated red cell destruction (60% recovery at 24 hours) had a negative MMA. Four control subjects with no atypical antibodies had normal autologous RBC 51 Cr recoveries and were negative by the MMA technique. The MMA test can be a reliable predictor of in vivo antibody behavior and an acceptable alternative to 51 Cr recovery studies. Immunohematology 1994;10:90–94.