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

The ⁵¹chromium (⁵¹Cr) 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, ⁵¹Cr 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 ⁵¹Cr 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 ⁵¹Cr 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 ⁵¹Cr recovery studies. Immunohematology 1994;10:90–94.