Tucson Medical Center Tucson, AZ 85712, Arizona, United States
Background/Case Studies: Reducing overall cost while reducing exposure to unnecessary Rh Immune Globulin (RhIg) has been a concern for both hospital and prenatal patients over the years. In 2018, we updated our prenatal policies such that certain Obstetric (OB) specimens would be sent out for RHD molecular testing. Our goal was to reduce current and future cost of unnecessary use of RhIg, limit patients’ exposure to pooled RhIg, nor misidentify RhIg candidates. An underlying goal was to help reduce potential Rh negative red blood cells (RBC) use if transfusion needs arose. This retrospective study reviewed all prenatal samples with molecular RHD genotyping from 2018 through 2022.
Study
Design/Methods: Our institution uses the NEO Iris and Echo Lumena instruments (Immucor, Norcross, GA) to perform ABO/Rh testing. When a result with the monoclonal anti-D4 or monoclonal anti-D5 demonstrated a greater than one strength difference in positive reactivity or if one anti-D clone was positive while the other tested negative, then the sample was retested by tube hemagglutination for verification. Samples were then referred for RHD molecular testing.
Results/Findings: During the 5-year period, 23,400 samples were processed and 38 prenatal samples qualified for RHD genotyping. Of 38 samples tested, 25 (65.8%) were found to be weak D type 1, 2, or 3 (Table 1) and no longer required RhIg based on the industry’s recommendations and our institution’s policies. Physicians were sent the recommendations and consulted with their patients for lack of need for RhIg or negative Rh units in the future. Conclusions: The reduction of unnecessary, potential biohazard exposure or misidentifying RhIg candidates is always a top priority for patient safety. In addition, with rising costs we deemed it essential to determine when RhIg may no longer be indicated for our prenatal patients based on previously published evidence regarding weak D types 1-3. This retrospective study supports that almost 70% of our molecular genotyped patients do not require RhIg and these patients may safely receive Rh Positive RBCs in the future while helping to protect our Rh Negative RBC supply.
Importance of research: This is a retrospective 5-year study to review the use of molecular testing to aid in the reduction of unnecessary biohazard exposure or misidentifying RhIg candidates as a priority for patient safety. With rising costs we deemed it essential to determine when RhIg may no longer be indicated for our prenatal patients based on previously published evidence regarding weak D types 1-3. This retrospective study supports that almost 70% of our molecular genotyped patients do not require RhIg.
