Thomas Jefferson University Hospital Philadelphia, Pennsylvania, United States
Background/Case Studies: Rh immune globulin (RhIG) is given to RhD-negative women of childbearing potential to prevent alloimmunization to the RhD antigen and subsequent hemolytic disease of the fetus and newborn (HDFN). Following administration, RhIG is detected on antibody identification panels as anti-D. Per the Rhogam package insert, “Anti-D detection in a patient’s plasma is dependent on assay sensitivity and time of sample collection post-injection.” Multiple articles have been published on the kinetics of RhIG; however, the rapidity with which RhIG can be serologically detected after administration has not been published.
Study
Design/Methods: Four case reports of RhD-negative women who received intramuscular (IM) RhIG and had anti-D detected on antibody identification panels after RhIG administration were retrospectively reviewed. These patients were identified by clinicians who inquired whether the anti-D identified on antibody identification panels was the result of alloimmunization or RhIG administration. In all cases, the clinician confirmed that the patient received RhIG just prior to antibody testing. Antibody identification testing was performed in solid-phase testing in all cases.
Results/Findings: Case #1 had anti-D serologically detected by solid-phase about 10.5 hours after RhIG administration. In case #2, RhIG was administered at 1725 and the specimen for type and screen was collected at 2342 (about 6 hours and 15 minutes later). Case #3 had anti-D serologically detected by solid-phase about 3 hours after RhIG administration. The patient in case #4 was given IM RhIG at 1302. The specimen for antibody identification was drawn 53 minutes after receiving RhIG, and the antibody identification panel detected anti-D with a strength of 1+. See Table 1. None of patients in these cases were known to be previously alloimmunized to the D antigen, and none of patients were known to have received RhIG in the preceding three months. Conclusions: RhIG can be serologically detected shortly after IM administration, with one case in our series occurring less than one hour after administration. The presence of anti-D on antibody identification panels shortly after RhIG administration can be explained by RhIG administration and may not indicate alloimmunization to the D antigen. Clinicians should be reminded to administer RhIG only after specimens for antibody identification have been procured.
Importance of research: A demonstration of how quickly RhIG may show up in an antibody screen has not yet been published. Although the typical workflow should be to collect a type and screen before RhIG is administered, this does not always happen. Therefore, it is helpful to know that RhIG can be detected quite rapidly after administration, and transfusion medicine physicians and clinicians should not be alarmed if this occurs.
