St Luke's Hospital Kansas City, Missouri, United States
Background/Case Studies: The accurate identification of D variants in patients is crucial for ensuring appropriate transfusion and immune-prophylaxis strategies. The AABB/CAP working group recommended in recent years to use two Anti-D reagents to assist in accurately determining the Rh status of patients.
By analyzing the performance of different anti-D reagents/methods compared to molecular testing results, an understanding of their efficacy in detecting D variants and their potential implications for clinical practice can be obtained. This retrospective study was to optimize method selection, test algorithms, and improve diagnostic accuracy in transfusion medicine.
Study
Design/Methods: The facility uses an automated analyzer to determine patients’ ABO/Rh type, Echo Lumena (Werfen, Norcross, GA). This analyzer currently employs 2 different anti-D clones (D4 & D5) using hemagglutination (Hemagg) method. We previous used a gel technology, QuidelOrtho (San Diego, CA). Any questionable/discrepant result was sent for molecular testing (Community Blood Center, Kansas City, KC) to provide a reference method and clarify the Rh status of the individual. This study compares molecular, gel and hemagg methods to analyze trends.
Results/Findings: During ~3 year study, 76 samples were sent for molecular testing. (Table 1). Of those tested with gel vs hemagg, 32 of the 33 gave 1+ to 3+ weaker reactions. Also, 18% of the identified variants were classified as weak partial D 4.0, capable of producing anti-D.
Conclusions: This retrospective study affirms the AABB/CAP Working group’s recommendation of utilizing two anti-D reagents in the accurate detection of D variants. The findings reveal a significant propensity of the gel reagent to overcall D variants as Rh positive. This misclassification poses a substantial risk, potentially leading to the omission of Rh prophylaxis and the mistransfusion of Rh-positive products. Notably, 18% of identified variants were weak partial D 4.0 types capable of producing anti-D. Such errors can set patients up for the formation of anti-D antibodies, compromising their future transfusion safety and pregnancy outcomes. The study underscores the necessity for careful reagent selection and incorporating molecular testing to improve transfusion practices for this population of patients.
