(P-TS-18) Anti-G Antibody Testing: A Single Center Retrospective Review with Implications for Obstetrical Management and Blood Bank Policy

Background/Case Studies: Blood bank policies for anti-G antibody testing remain variable, despite its critical role in obstetric care. Identification of anti-G has major implications, including prevention of severe hemolytic disease of the fetus and newborn and appropriate administration of Rh immune globulin. It is important to distinguish anti-G from anti-C and anti-D combinations as they appear similar but have different clinical implications. Our institution’s policy follows a stepwise algorithm, with anti-G testing performed at the reference laboratory when patients with pregnancy or pregnancy potential demonstrate presumptive anti-C and anti-D on initial in-house antibody identification. We conducted a retrospective review of all anti-G cases at a single institution to evaluate this approach.

Study

Design/Methods: Cases of Anti-G alloantibody identification were extracted systematically from the blood bank laboratory information system (BB-LIS; Sunquest) between 1/1/2012 and 4/31/2025. Case demographic and clinical data were obtained through chart review (Epic Systems) by transfusion medicine and obstetrics specialists.

Results/Findings: 14 patients with anti-G were captured by BB-LIS data extraction, of whom 12 were pregnant or of reproductive age females, with an age range from 29 to 44. In addition to anti-G, 6 (50%) patients had true anti-D and anti-C confirmed; 4 (34%) patients had only true anti-D; 1 (8%) patients had only true anti-C; 1/12 (8%) patients had only anti-G without anti-D or anti-C. Rhogam was administered to one patient who remained a candidate since anti-G but no true anti-D was identified. One additional patient received Rhogam even with the presence of anti-D. Intrauterine transfusions (IUT) were required in 10/12 (83%) patients who had anti-G in addition to anti-D and/or anti-C antibodies. Anti-G clinical testing is essential for risk stratification and obstetrical management, particularly as it relates to confirming a true anti-D. In cases of anti-G with anti-D (4/12; 34%), all pregnancies required intrauterine transfusions. In 2 cases where anti-G was identified and true anti-D was ruled out, one of the patients received Rhogam, and the other didn’t receive Rhogam as the neonate was determined to be RhD negative.

Conclusions: Anti-G antibody testing plays a critical role in obstetrical management, including in directing the appropriate use of Rhogam and avoiding unnecessary procedures such as IUT. Our findings highlight the importance of distinguishing anti-G from concomitant anti-D and anti-C antibodies. To optimize care for alloimmunized pregnant patients, standardized policies across institutions are warranted to ensure timely and consistent anti-G testing when presumed anti-D and anti-C are identified.