THE ROUTINE USE OF RH-NEGATIVE REAGENT RED-CELLS FOR THE IDENTIFICATION OF ANTI-D AND THE DETECTION OF NON-D RED-CELL ANTIBODIES

Background: Before 1987, fewer than 50 patients per year at the author s' laboratory had a positive antibody detection test due to antepartum Rhesus immunoprophylaxis. However, after 1987, a marked Increase was observed in the number of patients who had received Rh immune globulin (RhlG) during pregnancy as part of routine antepartum Rh immunoprophy laxis. In anticipation that an increased use of RhlG during pregnancy would increase the number of patients in whom anti-D was detected by t his laboratory, a protocol was developed to abbreviate the process req uired to identify anti-D. Although this protocol was adapted primarily to address an anticipated increase in antenatal RhlG usage in women, it was also applied to alloimmunized Rh-negative males. Study Design a nd Methods: When an Rh-negative patient (male and female) had a reacti ve screening test for unexpected antibodies and met certain other crit eria, the patient's serum was tested with a three-vial set of Rh-negat ive reagent red cells (Rh-negative screening RBCs), instead of with pa nels of typed RBCs (panel RBCs), for the identification of anti-D or t he detection on non-D antibodies. If the serum under test did not aggl utinate or hemolyze Rh-negative screening RBCs, anti-D was identified and no further testing was performed. If the serum agglutinated or hem olyzed Rh-negative screening RBCs, conventional testing with panel RBC s was done to determine the antibody specificity. Results: Rh-negative patients (n = 1174) who had reactive screening tests for unexpected a ntibodies were tested with Rh-negative screening RBCs; 1079 were found to have anti-D as a single antibody. Seven of these patients subseque ntly developed a non-D alloantibody, after transfusion or pregnancy, a nd one patient had anti-C that escaped detection at the time of initia l testing with Rh-negative RBCs (a false-negative result). Ninety-two patients had anti-D antibody but not anti-D. Use of the anti-D identif ication protocol actually reduced the laboratory workload by 176 Colle ge of American Pathologists workload units per month, in spite of a ma rked increase in the number of patients in whom anti-D was detected. N o hemolytic transfusion reaction was attributed to the abbreviation of anti-D identification. Conclusion: The identification of anti-D may b e abbreviated without jeopardizing patient safety. Such a protocol can reduce laboratory workload and might be particularly appealing to hea lth care facilities that perform antibody detection testing on large n umbers. Rh-negative pregnant women, especially if antepartum RhlG is a dministered routinely.